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Additional Physics > Topic 2 - Controlling and Using Electric Current > Flashcards

Topic 2 - Controlling and Using Electric Current Flashcards

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1
Q

What is current?

A

Rate of flow of charge around a circuit

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2
Q

What does there need to be in a circuit in order for a current to flow?

A

A voltage across the circuit

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3
Q

What is the unit to measure current?

A

Ampere, A

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4
Q

What is voltage?

A

Potential difference, driving force that pushes current around, like electrical pressure

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5
Q

What is the unit to measure voltage?

A

Volt, V

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6
Q

What is resistance?

A

Anything in the circuit which slows the flow down

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7
Q

What is resistance measured in?

A

Ohm, Ω

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8
Q

What happens to current if you increase the voltage?

A

More current will flow

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9
Q

What happens to current if you increase the resistance?

A

Less current will flow

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10
Q

Potential difference is ______ transferred per ____ ______.

A

Potential difference is energy transferred per unit charge

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11
Q

In a circuit, where is the energy supplied to the charge and how does this affect the voltage?

A
  • Power source

- Increases it

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12
Q

What causes charge to decrease in a circuit?

A

When voltage decreases my components in the circuit e.g. resistors

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13
Q

If the change in voltage is bigger, how does this affect the amount of energy transferred for a given charge passing through the circuit?

A

More energy

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14
Q

What is 1 volt in joules/coulombs?

A

1

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15
Q

How does current change around a circuit?

A

It doesn’t, current is conserved; the total current entering a junction id = to total current leaving a junction

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16
Q

What does an ammeter measure?

A

The current flowing through the component in amps

17
Q

How should an ammeter be put into the circuit?

A

In series

18
Q

What does a voltmeter measure?

A

Voltage/potential difference across the component in volts

19
Q

How should a voltmeter be placed in a circuit?

A

In parallel around the component under test

20
Q

What is the effect of a variable resistor on the current?

A

Alters the current flowing through the circuit which can be recorded by ammeter/voltmeter, plot on voltage-current graphs

21
Q

How does a diode affect current?

A

Current only flows through a diode in one direction

22
Q

How does a filament lamp affect current?

A

As temp increases, resistance increases

23
Q

What si the relation between current through a resistor and voltage?

A

Propotional

24
Q

What is the equation linking voltage, current and resistance?

A

Potential difference = current x resistance

25
Q

How does an LDR affect resistance?

A
  • Light dependent resistor
  • Amount of resistance depends on how light it is
  • In bright light, resistance falls
  • In darkness, resistance higher
26
Q

How does a thermistor affect resistance?

A
  • Temperature dependent resistor
  • Hot: resistance drops
  • Cold: resistance increases
27
Q

Why do resistors get hot when an electric current passes through them?

A
  • Energy transfer heats resistor
  • Energy transfer due to electrons colliding w/ ions in lattice that make up resistor as move through it
  • Collisions give ions in lattice extra energy emitted as heat increasing resistor’s resistance reducing curent flow (or more voltage for same current); if too hot, no current flows
  • Heating causes circuits to be less efficient as energy wasted. Can cause components to melt (circuit stops working)
  • Fuses use this effect to protect circuits: melt + break circuit if current gets too high
28
Q

What are the advantages of the heating effect in a resistor?

A
  • Good if you want to heat something
  • e.g. toasters
  • Current passes through coil, temp. increases so much so it glows + gives off infrared (heat) radiation that cooks bread
  • Light bulbs work in similar way
29
Q

How does an appliance with a high power rating transfer energy?

A

Transfers lots of energy in a short time

30
Q

What is power measured in?

A

Watts, W

31
Q

What is the equation linking electrical power potential difference and current?

A

Electrical power = potential difference x current

32
Q

What is the equation linking energy transferred, current, potential difference and time?

A

Energy transferred = current x potential difference x time

Additional Physics (6 decks)

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