Book edition 1st Edition

Author(s) Paul Peter Urone

Pages 1272 pages

ISBN 9781938168000

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Short Answer

Refer to Figure 21.7 and the discussion of lights dimming when a heavy
appliance comes on. (a) Given the voltage source is 120 V , the wire resistance is $0.400 Ω$ , and the bulb is nominally 75.0W , what power will the bulb dissipate if a total of 15.0 A passes through the wires when the motor comes on? Assume negligible change in bulb resistance. (b) What power is consumed by the motor?

(a)The power will the bulb dissipate if a total of 15.0 A passes through the wires when the motor comes on is $66.8 W$ .

(b) The power consumed by motor is 1644 W.

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Step by Step Solution

TABLE OF CONTENTS :

TABLE OF CONTENTS

Step 1: Definition of Power

Electric power is the percentage of time it takes to work or generate energy and is expressed as the work W or the transmitted energy divided by the time interval t.

Step 2: Calculating P2

(a)

Calculating resistance in the bulb,

$R_{Bulb} = \frac{E^{2}}{P_{1}} = \frac{{(120 V)}^{2}}{75 W} = 192 Ω$

Next step is calculating current flowing through bulb when motor comes on:

$I_{2} = \frac{E - {IR}_{wire}}{R_{Bulb}} = \frac{120 V - (15.0 A \times 0.400 Ω)}{192 Ω} = 0.59 A$

Finally, power in the bulb with motor on is:

$P_{2} = I_{2}^{2} R_{b} = {(0.59 A)}^{2} \times 192 Ω = 66.8 W$

Therefore, the power will the bulb dissipate if a total of 15.0 A passes through the wires when the motor comes on is 66.8 W.

Step 3: Power consumed by motor

(b)

To calculate power consumed by the motor we need to calculate current going through the motor:

$I_{3} = I - I_{2} = 15.0 A - 0.59 A = 14.41 A$

Next, resistance of the motor can be calculated as:

$R_{m} = \frac{E - {IR}_{1}}{I_{3}} = \frac{120 V - (15.0 A \times 0.400 Ω)}{14.41 A} = 7.92 Ω$

Finally, power of the motor is:

$P_{m} = I_{3}^{2} Rm = {(14.41 A)}^{2} \times (7.92 Ω) = 1644 W$

Hence, the power consumed by motor is 1644 W.

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College Physics (Urone)

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Short Answer

Step by Step Solution

Step 1: Definition of Power

Step 2: Calculating P2

Step 3: Power consumed by motor

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College Physics (Urone)

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Short Answer

Step by Step Solution

Step 1: Definition of Power

Step 2: Calculating P2

Step 3: Power consumed by motor

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