The figure depicts a length of model-railway track connected to a battery, a resistor and a relay coil. When no train is on the track, current flows in the relay coil, which makes a switch operate and turn on a light. When a train is in that section of track, most of the current travels through the train’s wheels and axles instead of through the relay coil. The switch in the relay then turns off the light. What is the reason for fitting a resistor between the battery and the track?
- Ato limit the heating of the wheels of the train
- Bto limit the energy lost in the relay coil when a train is present
- Cto prevent a short circuit of the battery when a train is present
- Dto protect the relay when a train is present