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National 5 physics > Electricity revision > Flashcards

Electricity revision Flashcards

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1
Q

what do electric fields cause other charges to experience?

A

A force

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2
Q

what charge does an atom nucleus have?

A

positive nucleus

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3
Q

what surrounds the nucleus?

A

Electrons

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4
Q

TRUE OR FALSE

in a conductor electrons movements are restricted

A

False

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5
Q

Current is measured in what?

A 
Amperes
current symbol (I)
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6
Q

Formula for charge?

A

Current X time

Q=IT

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7
Q

What should you remember when dealing with time?

A

Convert to seconds

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8
Q

What device is current measured with?

A

Ammeter

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9
Q

TRUE OR FALSE?

Current is not the same at every point in a series circuit

A

False

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10
Q

How many paths can an electron take in a series circuit

A

One

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11
Q

TRUE OR FALSE?

We can express this rule for current in series circuits using symbols: Is = I1 = I2

A

True

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12
Q

TRUE OR FALSE?

A parallel circuit is one in which there is more than one path for the electrons to take

A

True

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13
Q

what is voltage (potential difference) (V) measured in ?

A

Volts

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14
Q

What is energy measured in?

A

joule(J)

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15
Q

how many volts = 1 joule per coulombs ?

A

1 Volt

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16
Q

What do we use to measure potential difference ?

A

Voltimeter, connected accross the component

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17
Q

TRUE OR FALSE?

The voltage across each component in a series circuit added up is NOT equal to the voltage of the cell/battery

A

False

We can write this in symbols as Vs = V1 + V2

18
Q

TRUE OR FALSE

Sometimes we need to combine our rules for series and parallel circuits to deal with mixed (complex) circuits

A

True

19
Q

TRUE OR FALSE ?

To work out total Resistance, we use RT = R1 + R2 + R3

A

True

20
Q

When adding a resistance to a series circuit, does the resistance increase or decrease?

A

Increase

21
Q

Does the value of the current in the series circuit increase or decrease when a resistence is added

A

Decrease

22
Q

what is the formula used in relation to ohms law

A

V=IR

23
Q

What does each letter stand for in V=IR

A

V is voltage measured in Volts (V)
I is current measured in Amperes (A)
R is resistance measured in Ohms (Ω)

24
Q 
Example 
Calculate the current in this equation 
v= 2V
I=?
R=1kΩ = 1000Ω
A

I= 0.002A or 2mA (multiply by 1000)

25
Q

What happens when there is a non Ohmic conductor

A

The resistance of metals increases with temperature. Hence some components (e.g. lamps) will not obey Ohm’s Law as they heat up when more voltage is applied.

26
Q

What does the power rating of an appliance tell us

A

The power rating of an appliance tells us how much energy it changes every second.
e.g. a 2200W kettle changes 2200J of electrical energy into heat every second.

27
Q

Power can be measured using?

A

Power = Energy P = E

Time t

28
Q

What is power measured in?

A

Watts (W) and time (t) must be in seconds

a watt is a joule/second

29
Q

What happens when a current and voltage are known through an appliance

A

When the current through an appliance and the voltage across it are known, the power can be calculated using:
Power = Current x Voltage
P = I x V (PIV)

30
Q

What is the fuse main purpose

A

The fuse protects the flex from overheating. It melts and breaks the circuit if the current gets too high.

31
Q

What is the general rule for fitting fuses to plugs for appliances

A

Power rating > 720W, use 13A fuse. Power rating < 720W, use 3A fuse.

32
Q

TRUE OR FALSE?

In a direct current, the electrons can flow in different directions

A

False

33
Q

TRUE OR FALSE

in alternating current, the flow of electrons is constantly changing directions to and from

A

True

34
Q

How do we measure Hertz ?

A

The number of times that the current changes direction every second is called the frequency of the AC supply and this is measured in hertz (Hz).

35
Q

What frequency is mains electricity ?

IMPORTANT

A

50Hz

36
Q

How can we identify electrical signals to confirm whether they are AC or DC

A

oscilloscope

37
Q

what does LED stand for

A

light emitting diode

38
Q

is LED an input or output device

A

An LED is an output device, changing electrical energy into light.

39
Q

How many ways can a current pass through an LED

A

One way

40
Q

Why is a resistor connected in series in an LED

A

Too much current will damage the LED so a resistor is added to reducde the current

National 5 physics (2 decks)

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