Electromagnetic Induction 01

As soon as the load is raised, the rotation speed of the motor will decrase. Then, by the formula:

Back e.m.f. = NBAω

With ω, the angular speed decreased, the back e.m.f. will also decrease.

Thus, by another formula:

E (cell) = IR + E (back) where I and R are the current and resistance of the armature resp.

With E (back) decreased, IR should increase under the assumption that E (cell) is constant.

So conclusively, the current (ammeter reading) will increase to a higher value.

This problem can be solved in a simpler manner using conservation of energy.

When the motor raises a load at constant speed, there is a gain in gravitational potential energy of the load in unit time. Hence, the power source (e.g. a battery) that runs the motor will need to increase its energy supplied to the motor. Since power output = voltage (of source) x current (given to motor), an increase of power given to the motor indicates an increase of current flowing to the motor from the source.

Therefore, the current will increase to a higher value.