Question

A toy train of mass 1 kg moves with a constant velocity of 8 $\frac{m}{s}$ when connected to a battery of 8 volts. Find the current in the circuit if the battery was connected for 4 s. Assume no energy loss due to friction.

• A. 1 A
• B. 2 A
• C. 3 A
• D. 4 A

Answer 1

The correct option is A

1 A

The electrical energy of the battery will be converted into mechanical energy.

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

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

qV = 32

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

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