Various new quantities are introduced in this chapter, each having associated units. Which of the following quantities is followed by the wrong SI unit for that quantity?
1.resistivity, m
2.temperature coefficient of resistivity, (C)-1
3.electric power, kWh
4.drift speed, m/s
[Ques. 2] An electric heater is operated with a potential difference of 100 V. If the heating element has a resistance of 20 ohms, what is the power output of the heater and what is the current through it when operating?
1.2000 W, 5A
2.2000 W, 25 A
3.500 W, 5 A
4.500 W, 25 A
[Ques. 3] Three resistors are connected in series in a circuit. The resistors A, B, and C have resistances R, 2R, and 3R, respectively. Which resistance dissipates the most power?
1.A
2.B
3.C
4.They all dissipate the same power when in series.
[Ques. 4] The critical temperature below which superconductors conduct so superbly is affected by
1.chemical composition, pressure, and conductivity at normal temperatures.
2.chemical composition, molecular structure, and conductivity at normal temperatures.
3.chemical composition, pressure, and molecular structure.
4.pressure, molecular structure, and conductivity at normal temperatures.
[Ques. 5] Which of the following best describes superconductors?
1.conductors that have less than half the resistivity of iron
2.conductors with essentially no resistance below a critical temperature, peculiar to each material
3.conductors which have a drop in their resistivity as their temperatures are lowered
4.Conductors are materials which are very useful in a variety of ways; hence the name superconductor.
[Ques. 6] A length of wire has a resistance R. The wire is then uniformly stretched to double its original length. What resistance results. Hint: When the wire is stretched, its volume remains constant.
1. R/2
2. R
3. 2R
4. more than 2R
[Ques. 7] The battery powering a light bulb is disconnected. As the light bulb's heat dissipates, how will the resistance and current change?
1.The resistance will decrease and the current will increase.
2.The resistance will increase and the current will be zero.
3.The resistance will increase and the current will decrease.
4.The resistance will decrease and the current will be zero.
[Ques. 8] Which of the following best describes the inner workings of conductors?
1.Electrons collide at random, experiencing a net change of position equal to zero, except when exposed to an external electric field.
2.The electrons start at one electrode and travel directly to the other electrode, stopping there.
3.The electrons' drift speed depends only on the material of the conductor and not on the voltage difference applied to it.
4.None of these choices is correct.
[Ques. 9] A resistor, R, is made out of a particular material with resistivity P. The cylindrically shaped resistor has length I and radius r. To get four times as much resistance in your resistor you could
1.make the radius four times as big.
2.make the radius half as big.
3.make the radius one quarter the size.
4.make the radius twice as big.
[Ques. 10] The potential difference across a resistor R, and the current running through it, both increase. We know that resistance
1.decreases.
2.increases.
3.remains the same.
4.changes in ways we cannot determine with the information given.
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