Question

When the speed of a d.c. motor increases the armature current ______

Options

• increases.

• decreases.

• does not change.

• increases and decreases continuously.

Answer 1

When the speed of a d.c. motor increases the armature current decreases.

Explanation:

With the increasing speed, ω increases. Thus current reduces due to an increase in the back e.m.f.

Also, according to Ohm's law,

I = `("V" - "e")/"R"` and e ∝ ω

Hence, as ω increases, e increases reducing the current.