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Q. 54

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Physics for Scientists and Engineers: A Strategic Approach with Modern Physics
Found in: Page 793

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Short Answer

For an ideal battery, closing the switch in FIGURE P28.54 does not affect the brightness of bulb A. In practice, bulb A dims just a little when the switch closes. To see why, assume that thebattery has an internal resistanceand that the resistance of a glowing bulb is.

a. What is the current through bulb A when the switch is open?

b. What is the current through bulb A after the switch has closed?

c. By what percentage does the current through A change when the switch is closed?

a. when switch is open current though A is

b. when switch is closed current through A is

c. percentage change in the current is

See the step by step solution

Step by Step Solution

Part (a) Step 1: Given information

We have given,

We have to the current through bulb A when the switch is open.

Step 2: Simplify

Using Kirchhoff voltage in the loop, Let current i is flowing.

Part (b) Step 1: Given information

we have to find the current through bulb A after the switch has closed.

Step 2: Simplify

The total resistance due to bulb will be

then current through the battery will be

Now using the Kirchhoff voltage rule in left loop

Part (c) Step 1: Given information

we have to find by what percentage does the current through A change when the switch is closed.

Step 2: Simplify

The change in the current when switch is closed

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