# Circuits and the percent change of current when the switch is closed

• ChrisWM
In summary, when the switch is open, the current through bulb A is 0.181 A. After the switch is closed, the current through bulb A decreases to 0.174 A. This is a change of 3.867%, with the current through bulb A decreasing by this percentage when the switch is closed. The difference between 0.174 and 0.181 has 3 significant figures.
ChrisWM
Homework Statement
By what percent does the current through A change when the switch is closed
Relevant Equations
final-initial/initial
For an ideal battery (r = 0 Ω), closing the switch in (Figure 1)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 the 1.50 V battery has an internal resistance r = 0.30 Ω and that the resistance of a glowing bulb is R = 8.00 Ω.

Part A: What is the current through bulb A when the switch is open? This answer was .181 A

Part B: What is the current through bulb A after the switch has closed? This answer was .174 A

Part C: By what percent does the current through A change when the switch is closed? This is where I am stuck, I've tried -3.86,-3.87,3.86,3.87,4.02, and -4.02 and they are all wrong. I've done . (174-.181)/.181, and (.181-.174)/.174 and got the answers in the previous sentence, and I tried both positive and negative.

Try 3.867% (together with the % symbol)

ChrisWM said:
Part C: By what percent does the current through A change when the switch is closed? This is where I am stuck, I've tried -3.86,-3.87,3.86,3.87,4.02, and -4.02 and they are all wrong. I've done . (174-.181)/.181, and (.181-.174)/.174 and got the answers in the previous sentence, and I tried both positive and negative.
How many significant figures are there in 0.174 - 0.181 ?

## 1. How does the percent change of current in a circuit change when the switch is closed?

The percent change of current in a circuit is directly related to the resistance of the circuit. When the switch is closed, the resistance of the circuit decreases, causing an increase in the current. This results in a higher percent change of current compared to when the switch is open.

## 2. What factors affect the percent change of current when the switch is closed?

The percent change of current is affected by the resistance of the circuit, the voltage source, and the type of switch used. A higher resistance will result in a lower percent change of current, while a higher voltage source and a more efficient switch will result in a higher percent change of current.

## 3. How do you calculate the percent change of current in a circuit?

The percent change of current can be calculated using the formula: (Iclosed - Iopen) / Iopen x 100%, where Iclosed is the current when the switch is closed and Iopen is the current when the switch is open.

## 4. Can the percent change of current be negative when the switch is closed?

Yes, the percent change of current can be negative when the switch is closed if the resistance of the circuit increases significantly. This can happen if there is a faulty component in the circuit or if the switch is not functioning properly.

## 5. How does the type of switch used affect the percent change of current?

The type of switch used can affect the percent change of current in a circuit. A more efficient switch, such as a solid-state switch, will result in a higher percent change of current compared to a mechanical switch. This is because solid-state switches have lower resistance and can handle higher currents without significant voltage drops.

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