1. What generally happens to the electrical resistance of an insulator when its temperature is increased?
A.
It generally decreases
B.
It always becomes zero
C.
It remains exactly constant
D.
It becomes infinite in every case
Correct Answer:
It generally decreases
Explanation:
In an insulator, increasing temperature provides more thermal energy for charge carriers, so its resistance generally decreases.
2. An insulator usually has what type of temperature coefficient of resistance?
A.
Negative
B.
Positive
C.
Always zero
D.
Infinite
Correct Answer:
Negative
Explanation:
The resistance of an insulator generally falls as temperature rises, so it has a negative temperature coefficient of resistance.
3. Why does the conductivity of an insulator generally increase when its temperature rises?
A.
More charge carriers gain sufficient thermal energy
B.
The insulator loses all its atoms
C.
The applied voltage automatically increases
D.
The material becomes a perfect conductor immediately
Correct Answer:
More charge carriers gain sufficient thermal energy
Explanation:
Heating supplies energy that can free a small number of charge carriers, causing the conductivity of the insulator to increase.
4. At low temperature, the resistance of an insulator is generally
A.
Very high
B.
Very low
C.
Exactly zero
D.
Equal to that of copper
Correct Answer:
Very high
Explanation:
At low temperature, very few charge carriers have enough energy to move, so an insulator has very high resistance.
5. When an insulator is heated, its resistivity generally
A.
Decreases
B.
Increases without limit
C.
Becomes zero immediately
D.
Remains unchanged for all temperatures
Correct Answer:
Decreases
Explanation:
Heating increases the number of thermally excited charge carriers in an insulator, which generally decreases its resistivity.
6. The increase in conductivity of an insulator with temperature is mainly due to an increase in the number of
A.
Free charge carriers
B.
Atoms in the material
C.
External batteries
D.
Insulating layers
Correct Answer:
Free charge carriers
Explanation:
As temperature increases, more electrons or holes become available for conduction, increasing the conductivity.
7. Compared with its resistance at room temperature, an insulator usually has a higher resistance at
A.
A lower temperature
B.
A much higher temperature
C.
Its melting temperature only
D.
Every temperature above room temperature
Correct Answer:
A lower temperature
Explanation:
Lower temperature produces fewer thermally excited charge carriers, so the resistance of an insulator is generally higher.
8. Which statement correctly describes the effect of heating an insulator?
A.
Its insulating ability generally decreases
B.
Its resistance always becomes zero
C.
Its number of atoms becomes zero
D.
Its temperature becomes independent of heating
Correct Answer:
Its insulating ability generally decreases
Explanation:
Heating increases the number of charge carriers, allowing more current to flow and reducing the material's insulating ability.
9. If the temperature of an insulator is reduced, its electrical conductivity generally
A.
Decreases
B.
Increases greatly
C.
Becomes infinite
D.
Changes into mechanical conductivity
Correct Answer:
Decreases
Explanation:
Cooling reduces the number of thermally excited charge carriers, so the electrical conductivity generally decreases.
10. Which relationship is generally true for an insulator as temperature increases?
A.
Resistance decreases and conductivity increases
B.
Resistance increases and conductivity increases
C.
Resistance decreases and conductivity decreases
D.
Both resistance and conductivity remain exactly constant
Correct Answer:
Resistance decreases and conductivity increases
Explanation:
Higher temperature creates more thermally excited charge carriers, causing resistance to decrease and conductivity to increase.
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