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Chapter 21: Q4CQ (page 771)

Why is the power dissipated by a closed switch, such as in Figure 21.43, small?

Short Answer

Expert verified

Due to the low resistance of a closed switch, the power dissipated is little.

Step by step solution

01

Definition of voltage

Voltage: It's the difference between two points鈥� electric potentials.

02

Given

Resistance of the switch when closedRclosed=0惟

Resistance of switch when openRopen=鈭�惟

Emf of the battery isE

The internal resistance of the battery isr

External resistance connected in series with the battery isR

Current in the circuit when the switch is closedlclosed

Current in the circuit when the switch is openlopen

03

Finding why the power dissipated by the closed switch is small

The power dissipated is given :

P=lclosed2RclosedP=lclosed20惟P=0W

Resistance is directly proportional to power. As a result, the lower the resistance, the lower the power dissipated.

Therefore, the resistance of a closed switch is so low, that the power dissipated is little.

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