Sample Mid-Term Exam

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) The reason that the white-hot sparks that strike your skin from a 4th-of-July-type sparkler don't harm you is because
A) the energy per molecule is high, but the total energy transferred is small.
B) the energy per molecule is very low.
C) they have a low temperature.


2) Heat energy is measured in units of
A) joules.
B) calories.
C) both of these


3) A substance can absorb heat energy by the process of
A) radiation.
B) convection.
C) conduction.
D) all of these


4) A good absorber of radiation is a
A) good reflector.
B) poor emitter of radiation.
C) good emitter of radiation.
D) none of these


5) Hydrogen and oxygen molecules in a sample gas have the same temperature. This means the hydrogen molecules, on average, have the same
A) kinetic energy, but more speed.
B) speed, but less kinetic energy.
C) speed and the same kinetic energy.
D) speed, but more kinetic energy.
E) kinetic energy, but less speed.


6) Which force binds atoms together to form molecules?
A) nuclear
B) centripetal
C) gravitational
D) electrical
E) none of these


7) Every proton in the universe is surrounded by its own
A) electric field.
B) gravitational field.
C) both of these
D) none of these


8) The electric field around an isolated electron has a certain strength 1 cm from the electron. The electric field strength 2 cm from the electron is
A) four times as much.
B) twice as much.
C) the same.
D) half as much.
E) none of these


9) Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a
A) north pole.
B) south pole.
C) north or south poleÑno difference really.


10) Which force field can increase a moving electron's speed?
A) electric field
B) magnetic field
C) both of these
D) none of these


Sample Problems
Heat Energy = (specific heat) x mass x (temperature change)
Heat of fusion of water is 80 calories per gram
Heat of vaporization of water is 540 calories per gram
Specific Heat of Water is 1 cal/gram degree

1. A pot of water containing 0.5 kg of liquid is heated on a stove. If the amount of heat applied to the water is 3000 calories, what will be the temperature change of the water?

2. A glass of water containing 0.5 kg of liquid has a temperature of 20 degrees Celsius. An ice cube of mass 10 grams is dropped into the water. When the ice cube melts, what will be the temperature of the water?

3. A 15 watt light bulb is connected to 1.5 volt circuit. What current flows in the circuit? If a second light bulb is added to the circuit in series, what current will flow?

4. The transformer at a power plant converts the voltage from the plant (1000 volts) to a much higher value (100,000 volts) for long distance transmission. If the plant supplies 500 megawatts of power, how much current flows in the long distance line?