CBSE Class 10 Science 2022 · Paper 31/3/2 · Question 15

Electricity 4 marks Medium

Study the following electric circuit in which the resistors are arranged in three arms A, B and C :

(a)Find the equivalent resistance of arm B.[1]
(b)Calculate the equivalent resistance of the parallel combination of the arms B and C.[1]
(c)(i)Determine the current that flows through the ammeter.[2]
(c)(ii)OR : Determine the current that flows in the ammeter when the arm B is withdrawn from the circuit.[2]

Answer

(a) Arm B:

R_{B} = 5 + 10 + 15 = 30 Ω

. (b) Arm C:

R_{C} = 10 + 20 + 30 = 60 Ω

; B and C in parallel:

\frac{1}{R _{B C}} = \frac{1}{30} + \frac{1}{60} = \frac{1}{20}

, so

R_{B C} = 20 Ω

. (c)(i) Arm A:

R_{A} = 5 + 15 + 20 = 40 Ω

; total resistance

R = 40 + 20 = 60 Ω

; current through the ammeter

I = \frac{6}{60} = 0.1

A. OR (c)(ii) With arm B withdrawn:

R^{'} = 40 + 60 = 100 Ω

, so the ammeter reads

I^{'} = \frac{6}{100} = 0.06

🔒 Step-by-step solution