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When current is flowing in a superconductor, which statement is not true?
- A. A battery is needed to keep the current going.
- B. Electrical charges are moving
- C. The resistance is zero.
- D. No power is given off in the form of heat.
- Correct Answer: Option A
When a superconductor’s temperature drops below the critical temperature, its resistance:
- A. equals that of a semiconductor of equal dimensions.
- B. increases by two
- C. drops to zero.
- D. reduces to one half.
- Correct Answer: Option C
Superconductivity was discovered by:
- A. Volta
- B. Ohm
- C. Onnes.
- D. Bednorz and Müller.
- Correct Answer: Option C
Consider some material that has been cooled until it has become a superconductor. If it is cooled even further its resistance will:
- A. increase.
- B. decrease
- C. stay constant and zero.
- D. None of the above.
- Correct Answer: Option C
Superconductors have been discussed as a means for electrical energy storage. Because they are resistanceless, a current once started in a loop would continue without loss. If a current of 1.0 ´ 104 A were started in a huge toroidal coil of radius 1.0 km and inductance 50 H, how much electrical energy (in kWh) could be stored?
- A. 300 kWh
- B. 480 kWh
- C. 690 kWh
- D. 840 kWh
- Correct Answer: Option C
Which process will double the power given off by a resistor?
- A. doubling the current while doubling the resistance
- B. doubling the current by making a resistance half as big
- C. doubling the current by doubling the voltage
- D. doubling the current while making the voltage half as big
- Correct Answer: Option B
Light bulb A is rated at 60 W and light bulb B is rated at 100 W. Both are designed to operate at 110 V. Which statement is correct?
- A. The 60 W bulb has a greater resistance and greater current than the 100 W bulb.
- B. The 60 W bulb has a greater resistance and smaller current than the 100 W bulb.
- C. The 60 W bulb has a smaller resistance and smaller current than the 100 W bulb.
- D. The 60 W bulb has a smaller resistance and greater current than the 100 W bulb.
- Correct Answer: Option B
A cook plugs a 500 W crockpot and a 1 000 W kettle into a 240 V power supply, all operating on direct current. When we compare the two, we find that
- A. Icrockpot < Ikettle and Rcrockpot < Rkettle.
- B. Icrockpot < Ikettle and Rcrockpot > Rkettle.
- C. Icrockpot = Ikettle and Rcrockpot = Rkettle.
- D. Icrockpot > Ikettle and Rcrockpot < Rkettle.
- Correct Answer: Option B
The unit of power (the rate of energy transformation), the watt, in an electric circuit is equivalent to which of the following?
- A. V A
- B. V/s
- C. V Ω
- D. A Ω
- Correct Answer: Option A
The current through a 10 Ohm resister is 2 Amperes. The power expended in the resistor is
- A. 0.2 Watts
- B. 5 Watts
- C. 20 Watts
- D. 40 Watts
- Correct Answer: Option D