Test 2 examples

At the same temperature, two wires made of pure copper have different resistances. The same voltage is applied at the ends of each wire. The wires may differ in

length. cross-sectional area. .amount of electric current passing through them

The equation I= ;ΔV / R is called __________.

ohms law

The electric field inside a 20-cmcm-long copper wire is 0.011 V/m .

22.32

On a sunny day, a rooftop solar panel delivers 75 WW of power to the house at an emf of 17 VV. How much current flows through the panel?

22.35

A 80 WW electric blanket runs at 24 V A)What is the resistance of the wire in the blanket? How much current does the wire carry?

22.38

The two lightbulbs in (Figure 1) are glowing. What happens to the brightness of bulb BB if bulb AA is removed from the circuit? Construct the correct explanation.

.23.1

When switch S in the figure is open, the voltmeter V of the battery reads 3.10 VV . When the switch is closed, the voltmeter reading drops to 2.92 VV , and the ammeter A reads 1.64 AA . Assume that the two meters are ideal, so they do not affect the circuit. (Figure 1) A) Find the emf EMF. B) Find the internal resistance r of the battery. C)Find the circuit resistance R.

11/27

An ammeter is connected in series to a battery of voltage VbVbV_b and a resistor of unknown resistance RuRuR_u (Figure 1). The ammeter reads a current I0I0I_0. Next, a resistor of unknown resistance RrRrR_r is connected in series to the ammeter, and the ammeter's reading drops to I1I1I_1. Finally, a second resistor, also of resistance RrRrR_r, is connected in series as well. Now the ammeter reads I2I2I_2. If I1/I0=4/5I1/I0=4/5, find I2/I0

12

In the circuit in (Figure 1), a 20-ohm resistor sits inside 108 gg of pure water that is surrounded by insulating Styrofoam. If the water is initially at temperature 11.3 ∘C∘C, how long will it take for its temperature to rise to 58.9 ∘C∘C? Use 4190 J/kg⋅∘CJ/kg⋅∘C as the specific heat of water, and express your answer in seconds using three significant figures.

14

Consider the combination of capacitors shown in the diagram, where C1 = 3.00 μF, C2 = 11.0 μF , C3 = 3.00 μF , and C4 = 5.00 μF (Figure 1) Find the equivalent capacitance CA of the network of capacitors. Two capacitors of capacitance C5 = 6.00 μF and C6 = 3.00 μF are added to the network, as shown in the diagram.(Figure 2) Find the equivalent capacitance CB of the new network of capacitors.

15

You need a capacitance of 50 μF, but you don't happen to have a 50 μF capacitor. You do have a 30 μF capacitor. What additional capacitor do you need to produce a total capacitance of 50 μF? Should you join the two capacitors in parallel or in series?

17/27

The capacitors in each circuit are fully charged before the switch is closed. Rank, from longest to shortest, the length of time the bulbs (resistors) stay lit in each circuit.

21 Resistance increases when you add resistors in series, and it decreases when you add them in parallel. Capacitance, on the other hand, increases when you add capacitors in parallel and decreases when you add them in series. Furthermore, the circuit with the longest time constant takes the longest time to discharge.

What is the current in the wire in (Figure 1)?

22.1 0

Rank in order, from largest to smallest, the resistances R1R1 to R5R5 of these wires.

22.10

How much electric potential energy does 1.9 μCμC of charge gain as it moves from the negative terminal to the positive terminal of a 1.4 VV battery?

22.13

A 9.0V battery supplies a 2.0mA current to a circuit for 5.0hr.a.) How much charge has been transferred from the negative to the positive terminal?

22.15

A wire with resistance RR is connected to the terminals of a 24 VV battery. a)What is the potential difference ΔVendsΔVends between the ends of the wire? b)What is the potential difference ΔVendsΔVends between the ends of the wire? c)What is the current II through the wire, if the wire has the resistance 2.0Ω2.0Ω? d) What is the current II through the wire, if the wire has the resistance 3.0Ω3.0Ω?

22.18

Will the bulb in (Figure 1) light? Explain.

22.2 No, because the terminals of the battery are connected to the same end of the lightbulb filament.

A 100 WW lightbulb is brighter than a 60 WW lightbulb when both operate at the same voltage of 120 VV. If, instead, they were both operated at the same current of 0.5 AA, which would be brighter? Select the correct answer and explanation.

22.21

A 9.0 VV potential difference is applied between the ends of a 0.80-mmmm-diameter, 35-cmcm-long nichrome wire. What is the current in the wire?

22.25

A resistor dissipates 0.25 WW when current of 20 mAmA passes through it. Part complete How much current would be needed for the resistor to dissipate 0.50 WW?

22.26

When running on its 11.4 VV battery, a laptop computer uses 8.3 WW. The computer can run on battery power for 4.0 hh before the battery is depleted. a. What is the current delivered by the battery to the computer? b. How much energy, in joules, is this battery capable of supplying? c. How high off the ground could a 75 kgkg person be raised using the energy from this battery?

22.41

A heating element in a toaster dissipates 500 WW when run at 140 VV .How much charge passes through the heating element in 1.0 minute?

22.43

Draw a circuit diagram for the circuit of (Figure 1). Choose the correct diagram

23.1, 23.2

What is the equivalent resistance of group (a) of resistors shown in the figure? (Figure 1) What is the equivalent resistance of group (b) of resistors shown in the figure?

23.10

Three resistors in parallel have an equivalent resistance of 10 ΩΩ . Two of the resistors have resistances of 30 ΩΩ and 60 ΩΩ . What is the resistance of the third resistor?

23.12

You have a collection of 1.0 kΩkΩ resistors. How can you connect four of them to produce an equivalent resistance of 0.25 kΩkΩ?

23.14

You have six 3.0 kΩ resistors. How can you connect them to produce a total equivalent resistance of 2.0 kΩ ?

23.16

Consider the circuit shown in (Figure 1). Suppose that EEE_cal = 7.0 VV . For the steps and strategies involved in solving a similar problem, you may view a Video Tutor Solution. A) Find the current through the resistor aa. B) Find the potential difference across the resistor a C) Find the current through the resistor bb. D) Find the potential difference across the resistor bb. etc

23.29

What is the current in the circuit of the figure? (Figure 1)

23.34

Which resistor in the figure dissipates the most power? (Figure 1)

23.35

A 7.0 μF capacitor, a 11 μF capacitor, and a 16 μF capacitor are connected in series. What is their equivalent capacitance?

23.37

A metal wire of resistance RRR is cut into two pieces of equal length. The two pieces are connected together side by side. What is the resistance of the two connected wires?

23.37 R/4

A)In (Figure 1), what is the magnitude of the current in the wire above the junction? Express your answer in amperes. B)Consider the wire above the junction: we are looking from the top of the figure. Does charge flow toward or away from the junction?

23.4

Which of the following would increase the speed of a nerve impulse along an axon? Decreasing the resistance between nodes

23.42

The current through the 30 ΩΩ resistor in (Figure 1) is measured to be 0.50AA. A) What is the emf EE of the battery?

23.5

A) What is the potential difference across the 10 ΩΩ resistor? B) What is the potential difference across the 20 ΩΩ resistor? C)Choose the correct graph of the potential as a function of the distance s traveled through the circuit, traveling clockwise from VV = 0 VV at the lower left corner.

23.6

Consider two separate circuits shown in (Figure 1). If the resistors and batteries in the figures and are all the same, which of the two circuits dissipates more total power? Construct the correct explanation.

23.6

A)What is the magnitude of the current in the 18 ΩΩ resistor in the figure? (Figure 1) B)What is the direction of the current in the 18 ΩΩ resistor in the figure?

23.7

Wires 1 and 2 are made of the same metal. Wire 2 has twice the length and twice the diameter of wire 1. a) What is the ratio ρ2/ρ1 of the resistivities of the two wires? b) What is the ratio R2/R1 of the resistances of the two wires?

Resistivity is an intrinsic property of a substance, so since the two wires are made out of the same metal their resistivities are the same. Doubling the length doubles L, so that change alone makes R2 = 2R1. Doubling the diameter quadruples the area, which means that change alone makes R2 = R1/4.Together, the net effect is that R2 = R1/2 and the ratio R2/R1 = 1/2.

A copper wire is stretched so that its length increases and its diameter decreases. What is the result?

The wire's resistance increases, but its resistivity stays the same.