Consider a loop of wire with a resistor. In the same plane, (with switch S closed) a long wire has a current I flowing from left to right. R I S If switch S is closed for a long period of time, and then suddenly opened, what is the direction of the induced current through R as the current I rapidly decreases

Solution :

The given figure is a loop of a wire with a resistor.

When the switch S is closed for long time and is suddenly opened, the direction of the induced current can be find out by using the rule of right hand screw. According to the right hand screw rule, the direction of the magnetic field at the loop is in the direction that points outwards. The strength of the current rapidly decreases as it is switch off and the magnetic flux that is linked with the loop wire will also decrease.

According to the Lenz's law, the direction of the induced current must be such the decrease in the magnetic flux.  It means the direction of the magnetic field must be outwards and also normal to the plane of the screen. The direction of the induced anti clockwise or from right to left in the resistance.

the answer is b, have negligible mass