CrktCT -9. The three light bulbs A, B, and C are identical. How does the brightness of bulbs B and C together compare with the brightness of bulb A?A) Total power in B+C = power in A.B) Total power in B+C > power in A.C) Total power in B+C < power in A.Answer: Use P = V2/Rtot For bulbs B and C, Rtot = 2R. Total power in B+C < power in A.CrktCT -10. Two light bulbs A and B are connected in series to a constant voltage source. When a wire is connected across B as shown, the brightness of bulb A ...A: increasesB: decreases, but remains glowingC: decreases to zero (bulb A goes completely dark, no current)D: remains unchanged Answer: Bulb A increases in brightness (since the current increases when B is shorted).CrktCT -11.A circuit with two batteries is shown below. The directions of the currents have been chosen (guessed) as shown. Which is the correct current equation for this circuit?V=12VAB CA) I2 = I1 + I3 B) I1 = I2 + I3C) I3 = I1 + I2D) None of these.Answer: I3 = I1 + I2 CrktCT -12.Which equation below is the correct equation for Loop 1?A) –V2 + I1R1 – I2R2 = 0 B) V2 + I1R1 – I2R2 = 0C) –V2 – I1R1 + I2R2 = 0 D) V2 + I1R1 + I2R2 = 0E) None of these.Answer: –V2 + I1R1 – I2R2 = 0CrktCT -13. Consider the circuit shown. If you want to measure the current thru bulb 3, how should the ammeter be attached?R2R1R3V1 V22I1I3ILoop 1.R2R1R3V1 V22I1I3ILoop 1.I3A) Pink B) Yellow C) Green D) BlueE) Two of the 4 positions can be used to measure bulb3’s current.Answer: B) YellowCrktCT -14. I) In the circuit shown, what does the voltmeter read?A: 6 VB: 3 VC: 2 VD: 0 VE: Voltmeter will "fry"Answer: 6 VNow you switch the voltmeter over to "amp" mode.(But you leave it in the same position in the circuit)What does the ammeter read?A: 6 A B: 3 AC: 2 A D: 0 AE: Ammeter will "fry"Answer: Ammeter will fry. Ideal ammeter haszero internal resistance. If you attach an ideal ammeter to a battery, you will get infinite V 4 1 2 3 A A A A Pink Yellow Green Blue 6 V 2 V 6 V 2 Acurrent.CrktCT -15. The light bulbs in the circuit are identical. When the switch is closed, switch 12 VBA 12 VA: bulb A glows, and bulb B changes brightnessB: bulb A glows, and bulb B stays the sameC: bulb A does not glow, and bulb B changes brightnessD: bulb A does not glow, and bulb B stays the sameE: Something else happensAnswer: bulb A does not glow, and bulb B stays the sameAfter the switch is closed, the voltage drop across bulb A is zero, while the voltage drop across B is 12VCrktCT -16.The light bulbs in the circuit are identical. When the switch is closed,A:both go out.B:both stay the sameC:the intensity of light bulb B increases.D:the intensity of light bulb B decreases.E: both bulbs burn out due to infinite (very large) currentAnswer: both stay the same.CrktCT -17.All batteries shown are identical (1.5 V)How do the brightnesses of the bulbs compare?(Look carefully at the orientation of thebatteries!) A: A is brighter B: A and B are the same brightnessC: A is on, but B is brighter D: A is off, so B is brighterE: Both bulbs are offAnswer: A and B are the same brightness, sinceboth have the same voltage across them. In A,two of the three battery voltages cancel. + -0 + - + - - A B +CrktCT -18. In the circuit shown, the two bulbs are identical.The switch is suddenly closed. What happens to the currents through points A and B?A: IA stays same, IB decreasesB: IA increases, IB stays the sameC: IA stays same, IB stays the sameD: IA increases, IB decreasesE: IA decreases, IB decreasesAnswer: IA increases, IB stays the same
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