For the solenoids shown in the diagram (which are assumed to be close to each other), the resistance of the left-hand circuit is slowly increased. In which direction does the current flow through the galvanometer in the right-hand circuit?
Correct answer: A. B to A
- A. B to A
- B. A to B
- C. There is no current
- D. Cannot be determined
Explanation
Increasing the resistance causes a decrease in the current on the left. This reduces the field strength for the solenoid B=µonI. By the right-hand rule, the field through the solenoid is directed to the RIGHT. Hence, in the right-hand circuit, since there will be fewer field lines directed to the right, there is an induced electric field that will produce a current in the wires to "replace" the lost field lines. This means that the current will be directed with the same orientation as the current in the left circuit and the galvanometer will deflect to the LEFT.
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