Topic 5 -Electricity and Circuits Flashcards

1
Q

What is current?

A

The flow of electric charge - the rate of flow of charge

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2
Q

When is the only time a current will flow through an electrical component?

A

If there is a potential difference across the component and if the circuit is complete

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3
Q

What is the unit for current?

A

Ampere (A)

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4
Q

What is potential difference?

A
  • The same as voltage
  • the driving force that pushes the charge around the circuit
  • the energy transferred per coulomb of charge that passes between two points in an electrical circuitry
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5
Q

What is the unit for voltage/potential difference?

A

Volt (V)

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6
Q

What is resistance?

A

Anything that slows the flow of the charge down

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7
Q

What is the unit for resistance?

A

Ohms (Ω)

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8
Q

How does the potential difference affect the current?

A

The higher the potential difference across a given component, the higher the current will be

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9
Q

How does resistance affect the current?

A

The greater the resistance of a component, the smaller the current

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10
Q

In metals what is current caused by?

A

The flow of electrons

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11
Q

What is the symbol for current?

A

I

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12
Q

What is the equation relating charge, current and time?

A

Charge = current x time

Q

I t

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13
Q

When does more charge pass around a circuit in a given time?

A

When a greater current flows

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14
Q

What is charge measured in?

A

Coulombs (C)

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15
Q

SYMBOL CARDS USING WEBSITE

A

SYMBOL CARDS USING WEBSITE

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16
Q

How can you calculate energy transferred from charge and potential difference?

A

Energy transferred = charge moved x potential difference

E = Q x V

17
Q

What is energy measured in?

A

Joules

18
Q

What is the potential difference across an electrical component?

A

The amount of energy transferred by that electrical component per unit of charge passed

19
Q

What is one volt equal to?

A

One joule per coulomb

20
Q

How can you calculate voltage from current and resistance?

A

Potential difference = current x resistance

V = I x R

21
Q

When an electrical charge flows through a component what does it have to do?

A

Do work against resistance

22
Q

What does work done against resistance cause?

A

An electrical transfer of energy

23
Q

What is work done equal to?

A

Energy transferred

24
Q

When a current flows through a resistor what happens? Why?

A
  • The resistor heats up
  • Because some of the energy transferred is dissipated to the thermal energy stores of the component and the surroundings - not all of the energy from work done against resistance is transferred usefully
25
Q

How is energy transferred to the thermal energy stores of a component and the surroundings?

A

The electrons collide with the ions as they flow through the lattice which makes up the resistor.

26
Q

Why does the current decrease as a resistor heats up if there is a given p.d.?

A

The more the ions vibrate, the more difficult it is for electrons to get through the resistor because there are more collisions

27
Q

What does p.d. stand for?

A

Potential difference

28
Q

What happens if a resistor gets too hot?

A

No current will be able to flow (apart from with thermistors)

29
Q

What happens to the resistance or a thermistor with an increase in temperature?

A

It decreases

30
Q

What do low resistance wires do to the energy dissipated to thermal energy stores when current flows between components?

A

Decrease the energy dissipated

31
Q

What circuit can you use to investigate the relationship between current, p.d. and resistance for a range of components?

A

A parallel circuit with a variable d.c. source of power with an ammeter in series and a voltmeter in parallel around any resistor

32
Q

What components can you investigate in a circuit to investigate the relationship between current, p.d. and resistance?

A

A filament bulb or a fixed resistor

33
Q

What does an ammeter measure?

A

The current flowing though a component in amps

34
Q

Where should an ammeter be placed in a circuit?

A

Anywhere in the main circuit but it must be in series, NEVER IN PARALLEL

35
Q

What does a voltmeter measure?

A

The potential difference across a component

36
Q

Where must a voltmeter be placed in a circuit?

A

In parallel with the component under test