CBSE Class 10 Science 2020 · Paper 31/5/2 · Question 30

(a) Ohm’s law: the potential difference $V$ across the ends of a given metallic wire in an electric circuit is directly proportional to the current $I$ flowing through it, provided its temperature remains the same; $V=IR$. (b) An ammeter is connected in series in the circuit, with its + terminal towards the + terminal of the cell, so that the whole current passes through it. (c) $E=P\times t=100\text{W}\times 60\text{s}=6000\text{J}$. (d) The ends of a diameter divide the wire into two halves of $2.5\Omega$ each, joined in parallel between the two points: $\frac{1}{R}=\frac{1}{2.5}+\frac{1}{2.5}=\frac{2}{2.5}$, so $R=1.25\Omega$.