Question

A dc motor with its rotor and field coils connected in series has an internal resistance of 3.2 Ω. When running at full load on a 120-V line, the emf in the rotor is 105 V. Part A What is the current drawn by the motor from the line? Express your answer using two significant figures.

Answer 1

Answer:

The current drawn by the motor from the line is 4.68 A.

Explanation:

Given that,

Internal resistance of the dc motor, r = 3.2 ohms

Voltage, V = 120 V

Emf in the motor, $\epsilon=105\ V$

We need to find the current drawn by the motor from the line. A dc motor with its rotor and field coils connected in series, applying loop rule we get :

$V=\epsilon+Ir$

I is current drawn by the motor

$I=\dfrac{V-\epsilon}{r}\\\\I=\dfrac{120-105}{3.2}\\\\I=4.68\ A$

So, the current drawn by the motor from the line is 4.68 A. Hence, this is the required solution.