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Physics > Electricity (AS) (AQA) > Flashcards

Electricity (AS) (AQA) Flashcards

1
Q

Define current

A

Rate of flow of charge around a circuit

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2
Q

Give the unit of current

A

Amperes (A)

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3
Q

Define potential difference

A

Work done (energy transferred) per unit charge

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4
Q

State the unit of potential difference

A

Volts (V)

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5
Q

Describe current and potential difference in a series circuit

A

Current is the same in each component

Potential difference is split between the components

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6
Q

Describe current and potential difference in a parallel circuit

A

Potential difference is the same in each component

Sum of the currents through each component = total current (current is split)

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7
Q

Define resistance

A

Resistance = V/I

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8
Q

Define charge carriers

A

Charged particles that move through a substance when a potential difference is applied to it

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9
Q

What are the charge carriers in a metal?

A

Delocalised electrons

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10
Q

What are the charge carriers in a solution (eg salt solution)?

A

Charged ions

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11
Q

What is charge (Q) measured in?

A

Coulombs (C)

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12
Q

Define 1 coulomb

A

1 coulomb (C) is the amount of charge that passes in 1 second when the current is 1 ampere

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13
Q

Define conventional current

A

The relative direction in which positive charges/ions flow in a circuit

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14
Q

What is the direction of conventional current?

A

+ –> -

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15
Q

What is the direction of electron flow?

A
  • –> +
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16
Q

Are anions attracted to the anode or cathode in electrolysis?

A

Anode (+)

17
Q

State Kirchoff’s First Law

A

The sum of the current entering a junction = the sum of current leaving it

(Conservation of charge)

18
Q

What are the advantages of parallel circuits?

A

Extra components can be added without affecting the output of the others
When one appliance breaks they don’t all fail

19
Q

State ohm’s law

A

The current (I) in a conductor is proportional to the potential difference (V) across it provided temperature is constantly

20
Q

What is the threshold voltage for a silicon diode and what does this mean?

A

Around 0.6V
This means that the diode conducts very easily in the forward direction above 0.6V, but very little below 0.6V or in the opposite direction

21
Q

Explain the shape of an I-V graph for a filament lamp

A

The graph is a curve because as current increases temperature increases so resistance increases (so voltage increases)

22
Q

Why is a resistor an ‘ohmic material’?

A

Because ohm’s law is obeyed (I is proportional to V, it is a straight line graph through the origin etc)

23
Q

Give the unit for resistivity

A

The ohm metre

24
Q

What is the defining characteristic of a superconductor?

A

The component has 0 resistivity/resistance

25
Q

When does a component become superconducting?

A

When it reaches its critical temperature

26
Q

Give two applications of superconductors

A

Produce very strong magnetic fields

Reduce energy loss in power transmission

27
Q

The resistance of metals increases with temperature; what is the term used to describe materials with this property?

A

Positive temperature coefficient

28
Q

Why do semiconductors have a negative temperature gradient?

A

The number of charge carriers increases with temperature for semiconductors

29
Q

Give two uses of thermistors

A

Temperature sensors

Plotting resistance-temperature graphs

30
Q

State Kirchoff’s 2nd Law

A

Sum of the EMF across a closed loop = sum of the pd drops across components in that loop

(Energy is conserved)

31
Q

Define EMF

A

Electromotive force is the energy transferred per unit charge from a source from one form to electrical energy

32
Q

How many electrons in one coulomb of charge?

A

6.25*10^18

Physics (2 decks)

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