Class 10 Science · Chapter 12

Magnetic Effects of Electric Current

170 Class 10 Science questions on Magnetic Effects of Electric Current from the NCERT textbook, NCERT Exemplar and CBSE board papers 2023–2026, each with its answer and a step-by-step solution.

NCERT exercises

Exercises (9) Intext Questions (Page 196) (1) Intext Questions (Page 200) (3) Intext Questions (Page 201) (3) Intext Questions (Page 203) (3) Intext Questions (Page 205) (3)

NCERT Exemplar exercises

Multiple Choice Questions (12) Short Answer Questions (12) Long Answer Questions (8)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 4 of 9

Q61 CBSE 2026
1. (a)Copy the diagrams ‘a’ and ‘b’ and mark the direction of the magnetic fields produced around the current-carrying conductors.
2. (b)Compare the strength of magnetic field at points (i) P and Q, and (ii) Q and R.
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Fields circle anticlockwise in a and clockwise in b (seen from above); the field at Q is twice that at P and R.
(a) The field lines are the circles already drawn round each conductor; the right-hand thumb rule fixes which way round they go. In diagram ‘a’ the current flows upwards, so seen from above the arrows run anticlockwise round the wire - along the near side of the loop they point to the right. In diagram ‘b’ the current flows downwards, so seen from above the arrows run clockwise, opposite to ‘a’, and both of its circles are marked the same way as each other. (b) Using $B \propto I / r$ : (i) at P the current is $1$ A at $r = 2$ cm while at Q it is $2$ A at the same $r = 2$ cm, so $B_{Q} = 2 B_{P}$ - the field at Q is twice as strong as at P. (ii) At Q and R the current is the same $2$ A, and $r_{R} = 4$ cm is twice $r_{Q} = 2$ cm, so $B_{Q} = 2 B_{R}$ - the field at Q is twice as strong as at R. Taken together, $B_{P} : B_{Q} : B_{R} = 1 : 2 : 1$ , so the fields at P and R are equal.

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Q62 CBSE 2026

How is an electromagnet made ? Write any two ways by which the strength of electromagnet can be increased.

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Wind insulated copper wire as a solenoid over a soft iron core and pass current; strength rises with more current or more turns.
An electromagnet is made by winding a large number of closely spaced turns of insulated copper wire, in the form of a solenoid, over a soft iron core, and passing an electric current through the coil from a battery through a plug key. While the current flows, the soft iron core is strongly magnetised and the whole arrangement behaves as a magnet with a north and a south pole; as soon as the current is switched off the core loses almost all of its magnetism. Two ways of increasing its strength: (i) increase the current flowing through the coil; (ii) increase the number of turns of the coil.

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Q63 CBSE 2026

Draw the pattern of magnetic field produced by a current-carrying circular loop and name the factors on which the magnitude of the magnetic field due to a current-carrying circular coil depends.

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The loop's field lines are concentric circles round the wire, nearly straight at the centre; the field depends on current, radius and turns.
Pattern: the magnetic field lines of a current-carrying circular loop are concentric circles round every part of the wire, lying in planes at right angles to it. The circles are small and crowded close to the wire and grow larger further from it. At the centre of the loop the arcs are so large that they are almost straight lines, all pointing the same way — perpendicular to the plane of the loop — so the field there is nearly uniform; its direction is given by the right-hand thumb rule (out of the page for an anticlockwise current). Factors: the magnitude of the magnetic field at the centre of a current-carrying circular coil depends on (i) the current $I$ through the coil — directly proportional; (ii) the radius $r$ of the coil — inversely proportional; and (iii) the number of turns $n$ of the coil — directly proportional, since the turns add their fields. In short, $B \propto \frac{n I}{r}$ .

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Q64 CBSE 2026

Draw the pattern of magnetic field lines produced by a straight current-carrying conductor and name the factors on which the magnitude of magnetic field, due to it, depends.

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Concentric circles round the wire; the field increases with the current and decreases with the distance from the conductor.
The magnetic field lines are concentric circles centred on the conductor and lying in the plane perpendicular to it. Their direction is given by the right-hand thumb rule - anticlockwise when seen from a point the current is coming towards - and the circles are crowded near the wire and farther apart away from it. The magnitude of the field depends on (i) the current $I$ in the conductor, the field increasing in direct proportion to it, and (ii) the perpendicular distance $r$ of the point from the conductor, the field decreasing as $r$ increases: $B \propto I / r$ .

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Q65 CBSE 2026

(A) A vertical wire is carrying a current in the upward direction. It is placed in a magnetic field, pointing towards the East direction. Find out the direction of force on the wire. (B) Out of the two current carrying circular coils, coil ‘A’ has 10 turns while coil B has 15 turns. Which of the two coils will produce a stronger magnetic field at its centre if same current is flowing through both the coils ? Explain with reason. (C) In the given figure, AB and CD are two magnetic field lines intersecting each other at point O. If a compass is placed at point O, what will happen ? State your conclusions.

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Force is towards North; coil B (15 turns) gives the stronger field; the compass cannot point two ways, so field lines never intersect.
(A) The force on the wire is horizontal and directed towards the **north**. By Fleming's left-hand rule, with the forefinger along the field (East) and the middle finger along the current (vertically up), the thumb points North. (B) Coil B, with $15$ turns, produces the stronger field. At the centre of a circular coil $B = \frac{μ _{0} n I}{2 r}$ , so with the same current and the same radius the field is proportional to the number of turns - each turn adds its own field in the same direction - and $B_{B} : B_{A} = 15 : 10$ , that is $1.5$ times as strong. (C) The figure shows the field at O in two directions at once, so a compass needle placed at O would have to point in two directions (along OB and along OD) at the same time. That is not possible, since a needle can settle in only one direction - the situation shown is unreal. Conclusions: the magnetic field at any point has a single definite direction, and therefore two magnetic field lines never intersect each other.

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Q66 CBSE 2026
1. (a)Describe an activity to show that a current carrying conductor, placed in an external magnetic field experiences a force.
2. (b)Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally towards the front wall from the back wall, is deflected by a strong magnetic field to your right side. Find the direction of the magnetic field.
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A rod between magnet poles is displaced when current flows, showing a force; the electron-beam field is vertically downwards.
(a) Suspend a small aluminium rod horizontally from a stand by two connecting wires so that it lies between the poles of a strong horseshoe magnet (north pole below, south pole above), and connect it in series with a battery, a key and a rheostat. When a current is passed, the rod is displaced sideways; when the direction of the current is reversed, or the poles of the magnet are interchanged, it is displaced in the opposite direction. This shows that a current-carrying conductor placed in a magnetic field experiences a force, whose direction depends on the directions of the current and the field (Fleming's left-hand rule). (b) The magnetic field is directed vertically downwards.

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Q67 CBSE 2026
On the basis of the given circuit arrangement, answer the following questions :
1. (a)What happens to the rod AB when the key K is closed and why ?
2. (b)Name and state the rule that determines this behaviour of the rod AB in the above situation.
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The rod carrying current B to A in the upward field is displaced sideways, to the left; Fleming's left-hand rule.
(a) When K is closed a current flows through the rod AB, from end B to end A. The rod is then a current-carrying conductor lying across the magnetic field of the horseshoe magnet, which in the gap is directed vertically upwards because the N pole is below the rod and the S pole above it. A current-carrying conductor placed in a magnetic field experiences a mechanical force perpendicular both to the current and to the field, so the freely suspended rod is displaced: it swings horizontally, at right angles to its own length, towards the left. Taking the plug out of K stops the current, the force vanishes and the rod returns to rest. (b) The rule is Fleming's left-hand rule. Stretch the thumb, the forefinger and the central finger of the left hand so that all three are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the central finger points in the direction of the current, then the thumb points in the direction of the force acting on the conductor, that is, in the direction in which the rod moves.

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Q68 CBSE 2026
1. (a)The pattern of magnetic field due to a current carrying wire depends upon the shape made by that wire. Justify.
2. (b)A current carrying straight wire AB is shown in the given diagram. Out of X, Y and Z on which point will the strength of magnetic field be maximum and why ?
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Wire shape decides the field pattern; the field is maximum at X, the point nearest the wire.
(a) Each small part of a current-carrying wire produces circular field lines around itself, so the overall field depends on how the wire is laid out. For a straight wire the field lines are concentric circles round the wire; for a circular loop they are small circles near the wire that become nearly straight lines at the centre, at right angles to the plane of the loop; for a solenoid they are parallel straight lines inside (a uniform field) and like those of a bar magnet outside. The same current thus gives different patterns for different shapes. (b) The field is maximum at X, because X is nearest the wire and the magnetic field of a straight current-carrying wire decreases as the distance from the wire increases (its field-line circles are closest together near the wire).

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Q69 CBSE 2026

What is the use of fuse in domestic electric circuits ? How is its role different from the role of a green coloured wire given in domestic electric circuits ? What will happen if an electrician installs a fuse with higher-rated value than prescribed for a given electric circuit ?

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A fuse breaks the circuit on excess current; the earth wire protects the user from shock; an over-rated fuse fails to protect.
Use of the fuse: a fuse is a safety device connected in series with the live wire of a domestic circuit. It is a short piece of wire of high resistivity and low melting point. If the current exceeds the rated value — because of overloading or a short circuit — the heat produced ( $H = I^{2} R t$ ) melts the fuse wire, the circuit is broken and the current stops, so the wiring and the appliances are protected from damage and from fire. Difference from the green wire: the green wire is the earth wire, connected to a metal plate buried in the ground and to the metal body of the appliance. It normally carries no current. If the live wire touches the metal body, it provides a low resistance path for that current to flow into the earth, keeping the body at the potential of the earth. So the fuse protects the **circuit** and the **appliances** from excessive current by breaking the circuit, while the earth wire protects the **user** from electric shock by conducting leakage current safely away; the fuse is in series in the live wire, the earth wire is attached to the metal casing. Higher-rated fuse: it will not melt at the current for which the circuit was designed, so during an overload or a short circuit the large current goes on flowing. The wiring, switches and appliances are overheated, the insulation may melt, the appliances may be damaged and a fire may be caused — the fuse fails to protect the circuit at all.

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Q70 CBSE 2026

(A) Write any two precautions to be taken to avoid electrical accidents. (B) State how these precautions prevent possible damage to the electric circuit.

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Fit a fuse in the live wire and earth metal-bodied appliances; the fuse breaks the circuit, earthing gives a low-resistance path.
(A) Two precautions: (i) Fit an electric fuse (or an MCB) of the proper rating in series in the **live** wire of every circuit and of every high-power appliance. (ii) Earth every metal-bodied appliance - connect its metal casing through the green earth wire and the third pin of a three-pin plug to a metal plate buried deep in the ground. (B) How they prevent damage to the circuit: The fuse is a short piece of wire of high resistivity and low melting point. If the current rises above the rated value because of overloading or a short circuit, the heat produced in it, $H = I^{2} R t$ , melts the fuse wire. The circuit is broken at once and the current stops, so the household wiring, the switches and the appliances are never heated to the point where their insulation melts, they are damaged or a fire starts. Earthing provides the metal body of the appliance with a path of very low resistance to the ground. If the live wire touches the casing, the body is held at the potential of the earth (about $0$ V), so nobody gets a shock; and because that path has a very low resistance the leakage current is large, so it melts the fuse and disconnects the faulty appliance before its damaged wiring can overheat. (Other acceptable precautions, with the same kind of explanation: do not overload one socket through a multi-plug; use only ISI-marked, properly insulated wires of adequate thickness; switch off the mains before repairs and never touch switches with wet hands.)

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Q71 CBSE 2026

State the role of fuse and earthing in domestic electric circuit. Suggest any two precautions to be taken to avoid electrical accidents.

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A fuse breaks the circuit when current exceeds the safe value; earthing prevents electric shock from a faulty metal-bodied appliance.
Role of fuse: a fuse is a safety device connected in series with the live wire. Its wire has a low melting point, so when the current rises above the safe (rated) value, because of overloading or a short circuit, the wire heats up, melts and breaks the circuit. This stops the current and protects the appliances and the wiring from damage and fire. Role of earthing: the metal body of an appliance is connected through the earth wire to a metal plate buried deep in the ground. If the live wire touches the metal body because of a fault, the current flows through this low-resistance path into the earth, the body stays at earth potential, and a person touching the appliance does not get a severe electric shock. Precautions (any two): (1) Do not overload a socket by connecting too many appliances to it. (2) Use a fuse or MCB of the correct rating. (3) Never touch switches or appliances with wet hands. (4) Use earthed three-pin plugs for appliances with metal bodies, and replace damaged or poorly insulated wires.

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Q72 CBSE 2026
1. (a)At every electricity point in the different rooms of a house, there is a potential difference of 220 V. How is this possible ? Write any one benefit of it.
2. (b)An electric heater rated 2 kW; 220 V is used in a room having electric circuit of current rating of 5 A. What will happen when you switch on the circuit ? Justify your answer with reason.
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The points are in parallel, so each gets 220 V; the heater draws 9.09 A, above the 5 A rating, so the fuse blows.
(a) All the electricity points (sockets and appliances) in the rooms are connected in parallel between the live wire and the neutral wire of the mains. In a parallel connection the potential difference across every branch equals the supply voltage, so each point gets the full $220$ V. Benefit (any one): each appliance works at the full voltage it is designed for, and each can be switched on or off independently without affecting the others. (b) The heater draws $I = \frac{P}{V} = \frac{2000}{220} = 9.09$ A, which is more than the $5$ A current rating of the circuit. The circuit is overloaded, so its fuse melts (or the circuit breaker trips) and the supply is cut off; the heater cannot be used on this circuit and should be connected to the $15$ A power circuit.

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Q73 CBSE 2026
Read the following passage and answer the questions that follow : H.C. Oersted demonstrated that every current-carrying wire produces magnetic field around it. The pattern of the magnetic field depends upon the geometrical structure the current carrying wire is folded into. When a current-carrying wire is kept in a magnetic field, it experiences a force. Magnitude of this force is maximum when direction of magnetic field is at right angles to the current-carrying wire. Some rules to determine the direction of magnetic field and force were given by scientists Maxwell and Fleming.
1. (a)What is the direction of magnetic field inside and outside a solenoid ?[1]
2. (b)Same electric current is flowing through three identical wires A, B and C. If wires A, B and C are making respectively angles $3 0^{\circ}$ , $6 0^{\circ}$ and $27 0^{\circ}$ with the magnetic field, which of the wires will experience maximum force and why ?[1]
3. (c)(i)Name and state the law which is required to find out the direction of force acting on a current carrying wire, kept in a magnetic field.[2]
4. (c)(ii)OR : Name and state the law which is required to find out the direction of magnetic field around the current carrying straight conductor.[2]
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Inside a solenoid the field is uniform; wire C feels maximum force at $27 0^{\circ}$ ; Fleming's left-hand rule gives force direction; OR right-hand thumb rule.
(a) Inside the solenoid the magnetic field lines are parallel straight lines running from the south-pole end to the north-pole end, so the field inside is uniform; outside, they run from the north-pole end round to the south-pole end, as for a bar magnet, and the lines form closed loops. (b) Wire C experiences the maximum force. The force is largest when the wire is at right angles to the magnetic field, and a wire making $27 0^{\circ}$ with the field is at right angles to it (a $27 0^{\circ}$ turn is a $9 0^{\circ}$ turn the other way); A and B, at $3 0^{\circ}$ and $6 0^{\circ}$ , are not. Since $F \propto sin θ$ , the forces are in the ratio $0.5 : 0.87 : 1$ . (c)(i) Fleming's left-hand rule: stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular. If the forefinger points along the magnetic field and the middle finger along the current, the thumb gives the direction of the force (motion) on the conductor. OR : (c)(ii) Right-hand thumb rule (Maxwell's corkscrew rule): hold the straight conductor in the right hand with the thumb pointing along the current; the direction in which the fingers wrap around the conductor gives the direction of the magnetic field lines, which are concentric circles.

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Q74 CBSE 2026
Read the following passage and answer the questions that follow : Bhoumik was playing with a magnetic compass near a current carrying spring-like device. He observed that the compass needle shows deflection whenever he goes close to the device. After observing it, he started running around the device. Now, he observed that the compass needle is continuously changing its direction and tries to orient itself along the North-South direction of the Earth.
1. (i)What is the similarity in the behaviour of a freely suspended bar magnet and a magnetic compass ?[1]
2. (ii)How can the magnitude and direction of the magnetic field of a solenoid be changed ?[1]
3. (iii)(a)Compare the magnetic field due to a current-carrying solenoid and a current-carrying straight wire made by stretching a solenoid.[2]
4. (iii)(b)OR : When a moving electron enters in a magnetic field, what will happen to its motion ? State the law required to explain your observation of moving electron in a magnetic field.[2]
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Both settle North-South; current sets the field's size and direction; a solenoid has a strong uniform field with poles, a straight wire weak circles.
(i) A magnetic compass is a small, freely pivoted bar magnet, so both behave alike: each comes to rest along the North-South direction with its north pole pointing towards the geographic North, and each is deflected when a magnet or a current-carrying conductor is brought near it. (ii) The magnitude of the field is changed by changing the current through the solenoid - a larger current (or more turns, or a soft iron core inside) gives a stronger field; the direction is reversed by reversing the direction of the current, which interchanges the north and south ends. (iii)(a) Solenoid: the field lines inside are parallel straight lines, so the field inside is strong and uniform; outside it is like that of a bar magnet, with a north pole at one end and a south pole at the other - the field lines run from the north pole to the south pole outside the solenoid and from the south pole to the north pole inside it. Straight wire (the solenoid stretched out): the field lines are concentric circles around the wire; the field is much weaker, is not uniform - it decreases with distance from the wire - and there are no poles. (iii)(b) The electron experiences a force at right angles to both its motion and the field, so it is deflected from its straight path: its direction of motion changes (it moves along a circular arc if it enters at right angles to the field) while its speed stays the same; an electron moving along the field lines is not deflected. The law is Fleming's left-hand rule: with the thumb, forefinger and middle finger of the left hand mutually perpendicular, if the forefinger points along the field and the middle finger along the current, the thumb gives the direction of the force - for an electron the current is opposite to its motion.

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Q75 CBSE 2026
1. (i)State the rule which gives the direction of force acting on a current-carrying conductor placed in a magnetic field.
2. (ii)What is a fuse ? Why is it called a safety device ?
3. (iii)Why are electrical appliances with metallic bodies connected to the mains through a three-pin plug, whereas an electric bulb is connected with a two-pin plug ?
4. (iv)What will be the direction of force experienced by the conductor AB due to the magnetic field, when current flows in the direction shown ? Name the law you applied to find the direction.
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Fleming's left-hand rule gives the force; a fuse protects the circuit; the earth pin prevents shock; the force on AB is into the paper.
(i) Fleming's left-hand rule: stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, the thumb points in the direction of the force (motion) on the conductor. (ii) A fuse is a safety device connected in series in the live wire: a short piece of wire of a metal or alloy of suitable melting point. When the current exceeds its rated value because of overloading or a short circuit, the heat produced ( $H = I^{2} R t$ ) melts the wire and breaks the circuit, so the wiring and appliances are protected from damage and fire - hence it is called a safety device. (iii) The third pin of a three-pin plug connects the metallic body of the appliance to the earth wire. If the live wire touches the body, the leakage current flows to the earth through this low-resistance path, the body stays at the potential of the earth and the user does not get a severe shock (the large current also blows the fuse). An electric bulb has no exposed metallic body - its outer part is glass, an insulator - so it needs no earth connection, and a two-pin plug (live and neutral) is enough. (iv) The force on AB acts perpendicular to the plane of the paper, directed into the paper (away from the reader). Law applied: Fleming's left-hand rule.

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Q76 CBSE 2026
1. (i)State the rules to determine the following : (I) Direction of magnetic field produced around a current-carrying straight conductor. (II) Direction of force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it.
2. (ii)(I) Draw the magnetic field lines due to a current-carrying solenoid. (II) Three points A, B and C are marked in the above given diagram of the current-carrying solenoid. Out of the three points A, B and C, at which point is the magnetic field strength maximum and at which point is it minimum ?
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Right-hand thumb rule gives field direction; Fleming's left-hand rule gives force; the solenoid's field is maximum at A (inside), minimum at B (outside).
(i) (I) Right-hand thumb rule: hold the current-carrying straight conductor in the right hand with the thumb pointing in the direction of the current; the direction in which the fingers wrap around the conductor gives the direction of the magnetic field lines. (II) Fleming's left-hand rule: stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular; if the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, the thumb gives the direction of the force (motion) on the conductor. (ii) (I) Inside the solenoid the field lines are parallel, evenly spaced straight lines (a strong, uniform field); outside they curve round from one end to the other like those of a bar magnet, one end acting as a north pole and the other as a south pole. (II) The magnetic field is maximum at A (inside the solenoid, where the field lines are closest together) and minimum at B (outside the solenoid, where they are far apart); at C, the end, it is in between.

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Q77 CBSE 2026
1. (i)The magnetic field lines due to two bar magnets X and Y are shown in the given diagram. If the magnet X is displaced towards magnet Y, will there be repulsion or attraction between them ? Justify.
2. (ii)A metallic conductor is suspended perpendicular to the magnetic field of a horseshoe magnet. The conductor gets displaced towards the left when a current is passed through it. What will be the effect on displacement of conductor if the : (I) Current through the conductor is increased ? (II) Horseshoe magnet is replaced by another stronger horseshoe magnet ? (III) Direction of current through the conductor is reversed ?
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Repulsion, as the facing ends are both north poles; more current or a stronger magnet increases the displacement, and reversed current reverses it.
(i) There will be repulsion. Field lines come out of a north pole and go into a south pole; in the diagram they come out of X at its right end and out of Y at its left end, so the two ends facing each other are both north poles, and like poles repel. (ii) (I) The displacement increases, still towards the left, because a larger current increases the force on the conductor. (II) The displacement increases, still towards the left, because a stronger magnet gives a stronger magnetic field and hence a larger force. (III) The conductor is displaced towards the right, because reversing the current reverses the direction of the force (Fleming's left-hand rule); the size of the displacement is unchanged.

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Q78 CBSE 2026
1. (i)What is a solenoid ? Draw a diagram showing the magnetic field pattern due to a current-carrying solenoid (inside and outside).
2. (ii)Name any two factors on which the magnitude of the magnetic field due to a current-carrying solenoid depends.
3. (iii)A current-carrying solenoid is stretched and converted into a straight wire carrying current. Draw a diagram showing the magnetic field pattern around it and mark the direction of the magnetic field.
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A solenoid's field is uniform inside and like a bar magnet's outside; a stretched solenoid gives concentric circular field lines.
(i) A solenoid is a coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder. Inside it the magnetic field lines are parallel straight lines running from its S end to its N end, so the field inside is uniform; outside, the lines leave the N end, curve round and enter the S end, a pattern just like that of a bar magnet, so that every line is a closed loop (see the diagram). (ii) The magnitude of the field depends on (1) the number of turns of the solenoid per unit length and (2) the strength of the current through it; a soft iron core placed inside increases it further. (iii) Stretched out, the solenoid is only a straight current-carrying wire: its field lines are concentric circles centred on the wire and lying in planes perpendicular to it, crowded near the wire and farther apart away from it. Their direction is given by the right-hand thumb rule - for a current flowing upward the circles run anticlockwise as seen from above (see the diagram).

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Q79 CBSE 2026
1. (i)Write the name and statement of the rule used to determine the direction of the : (I) force experienced by a straight current-carrying conductor placed in a uniform magnetic field perpendicular to the field. (II) magnetic field produced around a straight conductor carrying electric current.
2. (ii)Differentiate between the magnetic field due to a bar magnet and the magnetic field due to a current-carrying solenoid.
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Fleming's left-hand rule gives the force and the right-hand thumb rule the field; a solenoid's field can be varied, a bar magnet's is permanent.
(i) (I) Fleming's left-hand rule. Stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, the thumb points in the direction of the force on the conductor (its direction of motion). (II) Right-hand thumb rule. Hold the current-carrying straight conductor in the right hand with the thumb pointing in the direction of the current; the fingers wrapped around the conductor then point in the direction of the magnetic field lines. (ii) Bar magnet: the field is permanent and always present; its strength is constant; the direction of its field cannot be changed without changing the orientation of the magnet. Current-carrying solenoid: the field is present only while the current flows; its strength can be changed by changing the magnitude of the current or the number of turns, or by inserting a soft iron core; the direction of its field can be changed by changing the direction of the current, which interchanges its poles. Outside, the two field patterns are alike, each having a north pole at one end and a south pole at the other.

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Q80 CBSE 2026
A person was repairing an electric heater. He observed that there were three different connecting wires of three different colours in the cable attached to the heater.
1. (i)What are these three different wires called ? Name them colourwise.
2. (ii)What is the value of standard potential difference at which electricity is supplied in Indian homes for lighting ?
3. (iii)What is the role of (I) earthing and (II) fuse in domestic electric circuits ?
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The wires are live (red), neutral (black) and earth (green); supply is 220 V; earthing prevents shock and a fuse stops excess current.
(i) The three wires are the live wire (positive), with red insulation; the neutral wire (negative), with black insulation; and the earth wire, with green insulation. (ii) $220$ V (alternating current, of frequency $50$ Hz). (iii) (I) Earthing: the earth wire joins the metallic body of the appliance to a metal plate buried deep in the earth. If the live wire touches the body, the leakage current flows to the earth through this low-resistance path, the body stays at the potential of the earth, and the user does not receive a severe electric shock. (II) Fuse: a short wire of low melting point, connected in series with the live wire. When the current exceeds the safe value because of overloading or short-circuiting, the heat produced melts the fuse wire and breaks the circuit, protecting the appliances and the wiring from damage and fire.

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