Electricity 2 Flashcards

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1
Q

List the factors that affect the heat produced in a current-carrying conductor.

A
  • Resistance
  • Current squared
  • Time
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2
Q

Define resistivity.

A

The resistance of the conductor of length 1m and cross-sectional area 1m2. The unit is ohm metre.

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3
Q

Name the device in the circuit that is used to vary the potential difference across the conductor.

A

A potential divide

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4
Q

Explain how the student used the potential divider to vary the potential difference.

A

Move the sliding contact to very the potential difference across the metallic conductor.

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5
Q

In an experiment to verify Joule’s law, explain why a fixed mass of water was used.

A

This experiment examines the relationship between current squared and temperature. All other variables such as mass of water must be held constant.

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6
Q

How would an observer know that a Wheatstone bridge is balanced?

A

The galvanometer would read zero. No current flows through the galvanometer.

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7
Q

What is a semiconductor?

A

A material with a conductivity or resistivity between that of a conductor and an insulator.

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8
Q

Distinguish between intrinsic and extrinsic conduction in a semiconductor.

A

I: The semiconductor is pure and the number of holes and electrons are equal.
E: The semiconductor is doped and the number of electrons and holes arae not equal.

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9
Q

Explain how a pure semiconductor can be converted into a p-type semiconductor.

A

Doping with a group III element.

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10
Q

Explain how a pure semiconductor can be converted into an n-type semiconductor.

A

Doping with a group V element.

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11
Q

What is the function of a rectifier?

A

Converts a.c. to d.c

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12
Q

What property of a diode makes it useful in a rectifier circuit?

A

Allows current to flow in only one direction.

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13
Q

Explain how a diode might be protected from having too large a current flowing through it when it is connected across a battery.

A

Connecting a resistor in series with the diode will protect it.

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14
Q

What would be the effect on the current flowing in this diode if the terminals of the battery were reversed. Explain your answer.

A

If the terminals of the battery are reversed either no current or a very small current flows, as the diode is now reversed biased.

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15
Q

What is meant by rms?

A

Root-mean-square

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16
Q

What is meant by a.c?

A

Alternating current