8 - Charge and current Flashcards

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1
Q

What is charge?

A

Charge is physical property that measures how charged something is.

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2
Q

What does the symbol “e” represent?

A

Elementary charge - the charge of one proton

1.6x10-19

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3
Q

How can electric current be defined?

A

The rate of flow of charge.

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4
Q

How do you calculate the number of electrons transferred?

A

Q/e

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5
Q

What is the direction of conventional current?

A

Positive to negative

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6
Q

What is an electrolyte?

A

A liquid that can carry an electric current, either due to being molten ionic compounds or in a solution.

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7
Q

What causes the flow of electrons in a metal wire?

A

Delocalised electrons being attracted to the positive end of the wire and repelled from the negative end of the wire.

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8
Q

What is Kirchhoff’s first law?

A

For any point in an electrical circuit, the sum of currents into that point is equal to the sum of currents out of that point.

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9
Q

What does the conservation of charge mean?

A

Electric charge can neither be created or destroyed. The total amount of electric charge in the universe is constant.

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10
Q

What is number density?

A

The number of free electrons per cubic metre of material.

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11
Q

Compare the number densities of conductors, semiconductors and insulators.

A
Conductors = high number density
Semiconductors = medium number density
Insulators = low number density
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12
Q

What is mean drift velocity (v)?

A

The average speed that charge carriers move at.

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13
Q

What equation links current and drift velocity?

A

I = Anev

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14
Q

Do batteries have charge?

A

No

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15
Q

What do batteries do to electrons?

A

Move them around the circuit.

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16
Q

What happens when a wire changes size?

A

The current must stay constant and the elementary charge and number density cannot change so the VELOCITY of the electrons changes proportionally to the size of the wire.

Larger area = slower velocity
Smaller area = faster velocity

17
Q

Define 1 coulomb.

A

The amount of charge that passes a point in 1 second when the current is 1 ampere.