Electricity Flashcards

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1
Q

What is current?

A

The rate of flow of charge

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2
Q

Where does an ammeter go and why?

A

In series due to having a negligible resistance

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3
Q

What is the formula for current?

A

I = Q/t

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4
Q

What is potential difference?

A

The energy transferred per coulomb of charge

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5
Q

Where does a voltmeter go and why?

A

Parallel due to having a very high resistance

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6
Q

What is the equation for working out voltage?

A

V=W/Q

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7
Q

What is Kirchoff’s law for current in series?

A

That it is the same throughout

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8
Q

What is Kirchoff’s law for current in a parallel circuit?

A

The current into the junction = the current out if the junction

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9
Q

What is Kirchoff’s law for potential difference in series?

A

The sum of the P.d = The total E.M.F

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10
Q

What is Kirchoff’s law for potential difference in a parallel circuit?

A

The P.d is the same across each branch

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11
Q

What is Kirchoff’s law for resistance in a series circuit?

A

R1 + R2 = Rtotal

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12
Q

What is Kirchoff’s law for resistance in a parallel circuit?

A

1/R1 + 1/R2 = 1/Rtotal

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13
Q

What is resistivity?

A

The resistance of a 1m^2, 1m long sample of material

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14
Q

What is resistivity in relation to the material?

A

It is a property

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15
Q

What is the equation for resistivity?

A

R=PL/A

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16
Q

What is resistivity affected by?

A
  1. Cross sectional area
  2. Material
  3. Length
  4. Temperature
17
Q

What is drift velocity?

A

The average speed particles travel along a conductor

18
Q

What is the equation for drift velocity?

A

I = nAvq

I = current 
n = charge carrier density
A = cross sectional area
v = drift velocity
q = charge
19
Q

What is resistance?

A

The degree to which a component impedes the flow of current

20
Q

How do you work out resistance?

A

R = V/I

21
Q

How do you measure resistance?

A

Using a multimeter

22
Q

What does a thermistor do?

A

A component thats resistance changes with temperature

23
Q

What does an LDR do?

A

A light dependant resistor works as light increase the resistance of the component decreases

24
Q

What is the equations for potential dividers?

A

L/L = Vout/Vsupply

25
Q

What is a positive temperature coefficient and how do they work?

A

Resistance increases as temperature rises, due to lattice ions vibrating and more electron colliding with the ions

26
Q

What is an Ntc and how does it work?

A

A negative temperature coefficient is where resistance goes down as temperature rises due to more conduction electrons being realised which allow for a higher current flow

27
Q

What is E.M.F?

A

The energy gained per coulomb of charge passing through the supply

28
Q

What is the internal resistance?

A

The resistance of the cell

29
Q

What is the terminal P.d?

A

The P.d between the cell terminals

30
Q

What are the lost volts?

A

The energy transferred per coulomb in moving through the cell

31
Q

How do you work out E.M.F?

A
E.M.F = Terminal P.d + Lost Volts 
E = V + Ir
32
Q

What is power?

A

Power is joules per second

33
Q

How does a fixed resistor I-V graph look?

A

Line if Y=X due to having a fixed resistance making it an ohmic conductor

34
Q

What does the I-V graph of a diode look like?

A

Flat line until a certain point on the X axis, due to a certain P.d needed for a change in current. Moreover current only flows in one direction

35
Q

What does the I-V graph of a filament bulb look like?

A

Looks like an f passing through the origin, due to as current increase, temperature increases meaning that more electron collisions occur due to lattice vibrations. Moreover it is a non-ohmic conductor