Question

A toy train of mass 1 kg moves with a constant velocity of 8 m/s, when connected to a battery of 8 volts for 4 s. is the current in the circuit .

• A. $1A$
• B. $2A$
• C. $3A$
• D. $4A$

Answer 1

The correct option is A $1A$

Electrical energy of the battery will be converted into mechanical energy.

Kinetic energy of the train = $\frac{1}{2}m{v}^2$ = $\frac{1}{2}\times 1\times 8^2$ = $32J$

This energy should be equal to the energy produced by battery which is $W=qV$

$qV=32J$

$q=\frac{32}{V}$ = $\frac{32}{8}$ = $4C$

Now current, $I=\frac{q}{t}$ = $\frac{4}{4}$ = $1A$