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electricity Flashcards

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1
Q

What is the relationship between resistance and current?

A

Inversely proportional- the greater the resistance, the smaller the current

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2
Q

What is current?

A

The rate of flow of charged particles measured in amperes

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3
Q

What is the equation for current?

A

Current=charge/time

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4
Q

What is charge?

A

a property of a body which experiences a force in an electric field, measured in coulombs

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5
Q

What is potential difference?

A

a measure of energy, per unit of charge, transferred between two points in a circuit, measured in volts

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6
Q

What is the equation for charge?

A

Charge = current x time

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7
Q

What is the equation for potential difference?

A

potential difference = current x resistance

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8
Q

What is resistance?

A

opposition to the flow of current, measured in Ohms

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9
Q

Describe the required practical investigating factors affecting resistance

A
  1. attach a crocodile clip to the wire level with 0 cm on the ruler
  2. Attach the second clip 10cm away
  3. close the switch then record the current and p.d using an ammeter and voltmeter
  4. open the switch and then repeat with the clip 10cm further along the wire
  5. calculate the resistance by dividing the p.d by the current
  6. plot on a graph
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10
Q

What is the equation for resistance?

A

resistance=potential difference/current

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11
Q

What does the IV graph for a resistor look like and what does it mean?

A

A resistor will have a straight line going through the origin showing that current and potential difference are directly proportional

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12
Q

What does the IV graph for a filament lamp/bulb look like and what does it mean?

A

straight line through the origin and curves once it reaches the limit of proportionality. As the current increases, the temperature of the filament increases, thus increasing the resistance, meaning less current can flow through

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13
Q

What does the IV graph for a diode look like and what does it mean?

A

a steep curve that turns into a straight line, only on one side of the graph represents current only flowing in one direction

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14
Q

What is an LDR?

A

Light dependent resistors decrease resistance in bright light and increase resistance in darkness

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15
Q

What is a thermistor?

A

A temperature dependent resistor- resistance decreases in hot conditions and increases in cold conditions

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16
Q

Describe the IV required practical

A
  1. set up a circuit with a variable resistor, a component and an ammeter and voltmeter
  2. take several readings of the ammeter and voltmeter, changing the variable resistor each time
  3. swap the wires to reverse the direction of current and repeat the readings
  4. plot the readings on a graph
17
Q

In a series circuit, how are resistance, current and potential difference distributed?

A

Potential difference is shared, current remains the same and resistance adds up

18
Q

In a parallel circuit, how are resistance, current and potential difference distributed?

A

Potential difference is the same, current is shared and resistance decreases by adding another resistor in parallel

19
Q

What happens to resistors in parallel ciruits?

A

If you have 2 resistors in parallel, their total resistance is smaller than the resistance of the smallest resistor as they have the same p.d acting against them but by adding another loop, current increases, thus decreasing resistance

20
Q

What will happen when you add identical resistors in series and how will that look like on a graph?

A

resistance increases, represented by a straight line through the origin

21
Q

What will happen when you add identical resistors in parallel and how will that look like on a graph?

A

Resistance will decrease, represented by a downwards curve that looks like a reciprocal curve

22
Q

Are mains and battery supply alternating or direct current?

A

Mains is alternating and battery is direct current

23
Q

What us the frequency and voltage of UK mains supply?

A

50 Hz and 230V

24
Q

What is the difference between alternating and direct current?

A

Alternating current is where current flows in both directions and positive and negative ends alternate whereas direct current always flows in the same direction

25
Q

What are the three different wires, their functions and colours?

A

the neutral wire is blue and completes the circuit, the earth wire is green and yellow and is a safety feature that protects the casing from becoming live and the live wire is brown and provides 230V of alternating current

26
Q

What is the equation for energy transfer in a circuit?

A

power x time

27
Q

What does the power rating on appliances mean?

A

The maximum safe power that they are able to operate at

28
Q

What is potential difference in terms of energy and charge?

A

p.d = energy/charge

29
Q

what is power in terms of p.d and current?

A

power= p.d x current

30
Q

What is the national grid?

A

A system of cables and transformers covering the UK, connecting power stations to consumers

31
Q

When does electricity demand increase?

A

In the morning when people get up, in the evening when people come home, in colder weather or popular events on TV

32
Q

What is the potential difference and the current like in the national grid and why?

A

There is a high potential difference and a low current as a lower current prevents overheating and loss of thermal energy to the surroundings, making it more efficient

33
Q

Why are transformers used?

A

To be able to deliver high potential difference of 400,000 V across the wires whilst delivering 230V to consumers more efficiently

34
Q

What is the equation for transformers?

A

p.d across coil 2 x current across coil 2 = p.d across coil 1 x current across coil 1

35
Q

What causes static electricity?

A

negatively charged electron transfer causes a potential difference and results in static electricity

36
Q

What causes static shocks?

A

as electric charge builds, large potential difference causes electrons to jump between the charged object and the earth or an earthed conductor - this is the spark

37
Q

What is electrostatic attraction/repulsion?

A

oppositely charged objects move towards each other without touching or similarly charges objects move away from each other

38
Q

What directions do field lines travel in?

A

positive to negative and at a right angle to the surface

39
Q

What causes sparks?

A

the high potential difference causes a strong electric field between the charged object and the earthed conductor, ionising electrons in the air particles between. This makes them more conductive and allows current to flow through

Physics (9 decks)

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