Physics Homework Chapter 18

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1. A battery having an emf of 11.00 V delivers 112 mA when connected to a 67.0  load. Determine the internal resistance of the battery.
_____Ω



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2. What is the equivalent resistance of the combination of identical resistors between points a and b in the figure below?
____R

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3. Three 10.0 Ω resistors are connected in series with a 9.0 V battery. Find the following.

(a) the equivalent resistance of the circuit
_____Ω

(b) the current in each resistor
_____A

(c) Repeat for the case in which all three resistors are connected in parallel across the battery.
equivalent resistance
_____Ω

current in each resistor
_____A



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4. Consider the circuit shown in the figure below. (R = 19.0 Ω.)

(a) Find the current in the R = 19.0 Ω resistor.
_____A

(b) Find the potential difference between points a and b.
_____V

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5. (a) Find the current in a 6.00 Ω resistor connected to a battery that has an internal resistance of 0.40 Ω if the voltage across the battery (the terminal voltage) is 21.00 V.
_____A

(b) What is the emf of the battery?
_____V



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6. The figure below shows a circuit diagram. (R₁ = 1460 , R₂

 = 570 , ΔV = 30.0 V)
(a) Determine the current. 
_____mA

(b) Determine the potential of wire A relative to ground. 
_____V

(c) Determine the voltage drop across the 1460  resistor.
_____V

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7. Consider the combination of resistors shown in the figure below.

(a) Find the equivalent resistance between point a and b.
_____Ω

(b) If a voltage of 41.9 V is applied between points a and b, find the current in each resistor.
12 Ω        _____A
6 Ω          _____A
5 Ω          _____A
4 Ω          _____A
8 Ω          _____A

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8. The ammeter shown in the figure below reads 1.50 A. Find I₁
, I₂, and ε. (Assume R = 7.50 Ω.)I₁  =     _____A
I
2  =     _____Aε=        _____V

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9. In the circuit of the figure below, the current I₁
 is 3.4 A and the values of ε and R are unknown. What are the currents I₂ and I₃?I₂
 =   _____AI₃
 =   _____A

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10. An uncharged capacitor and a resistor are connected in series to a source of emf. If ε = 7.00 V, C = 25.0 µF, and R = 100 Ω, find the following:
(a) the time constant of the circuit
_____s

(b) the maximum charge on the capacitor
_____µC

(c) the charge on the capacitor after one time constant
_____µC


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11. Consider a series RC circuit for which R = 4.0 MΩ, C = 8.0 µF, and ε = 25 V. Find the charge on the capacitor 10 s after the switch is closed.
_____µC

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12. A charged capacitor is connected to a resistor and a switch as in the figure below. The circuit has a time constant of 1.00 s. Soon after the switch is closed, the charge on the capacitor is 80.0% of its initial charge.

(a) Find the time interval required for the capacitor to reach this charge.
_____s

(b) If R = 220 kΩ, what is the value of C?
C =   _____µF

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13. What minimum number of 100 W lightbulbs must be connected in parallel to a single 180 V household circuit to trip a 40.0 A circuit breaker? 
_____lightbulbs


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