Q.

A DC motor operates with 220 V mains. Initially, it draws a current of 20 A. the resistance of the starter is 6Ω. When the motor runs at its full speed it consumes 500 W power. Find the current drawn by it.

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a

10 A

b

15 A

c

5 A

d

20 A

answer is B.

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Detailed Solution

The motor is listed as running at 220 V. When operating at full speed, the initial current and power are both provided, therefore we must now take into account the emf and potential difference independently.

Using ohm’s law V=Ir

220=20×r
r=11Ω
Consequently, the resistance manifests as 11Ω, additionally, given that the starter's resistance is 6Ω. The result is that the circuit's overall resistance is 11Ω the starter's reluctance, though, (11-6)=5Ω
The motor's current consumption when operating at maximum speed must now be determined. 500 W of power.
Using the formula, P=i2R
500=i2×5

i=10 A

Hence, the correct answer is option B.

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A DC motor operates with 220 V mains. Initially, it draws a current of 20 A. the resistance of the starter is 6Ω. When the motor runs at its full speed it consumes 500 W power. Find the current drawn by it.