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a level physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is effective resistance

A

the measure of the resistance of all the resistors throughout the circuit.

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2
Q

Current vs voltage graph for a wire

A
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3
Q

Current vs voltage graph for a lamp

A
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4
Q

Current vs voltage graph for a thermistor

A
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5
Q

Current vs voltage graph for a diode

A
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6
Q

Diode and light emitting diode diagram

A
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7
Q

Resistor, variable resistor, thermistor and light dependant resistor diagrams

A
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8
Q

Heater diagram

A
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9
Q

Electric motor diagram

A
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10
Q

What is an ohmic conductor

A

A conductor that obeys Ohm’s Law

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11
Q

What is a LDR also known as and when is its resistance highest?

A

Photocell - when the light intensity is lowest

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12
Q

Graphs for a capacitor (charge, voltage and current)

A
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13
Q

What is the electromotive force

A

The potential difference across the terminals of a battery when no current flows

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14
Q

What are lost volts

A

The voltage used to overcome the internal resistance of the battery

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15
Q

What is the terminal voltage

A

The voltage delivered to the load resistance in the circuit (the p.d when no current flows; the terminal voltage is the p.d when current flows)

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16
Q

Equation linking charge current and time taken for a capacitor to reach the charge

A

Q=I x t

17
Q

describe in terms of electron flow what is happening when a capacitor charges up

A

Capacitors are charged by a power supply (e.g., a battery)
One plate of the capacitor is connected to the positive terminal of the power supply
The positive terminal ‘pulls’ electrons from this plate
Hence the plate nearest the positive terminal becomes positively charged
These electrons travel around the circuit and are pushed from the negative terminal of the power supply
The negative terminal ‘pushes’ electrons onto the other plate
Hence the plate nearest the negative terminal becomes negatively charged
As the negative charge builds up, fewer electrons are pushed onto the plate due to electrostatic repulsion from the electrons already on the plate
When no more electrons can be pushed onto the negative plate, the charging stops

18
Q

How are capacitors used?

A
19
Q

What is the time constant of capacitance

A

Time taken for charge or potential difference to increase by 63% OR fall by 37%

20
Q

Capacitance def

A

Charge stored per unit potential difference

21
Q

Graphical method for measuring time constant of capacitance

A
22
Q

Mathematical method for calculating the time constant of capacitance

A
23
Q
A
24
Q

What is one farad equal to?

A

1 coulomb per volt (C/V)

25
Q

What is the energy store in a capacitor

A
  • Electric potential energy
  • it is the energy stored in the electric field formed by the oppositely charged plates
26
Q

Calculating the energy stored in a capacitor graphically

A
27
Q

Dielectric material def

A
28
Q

What do the components of this equation mean?

A
29
Q

What do the components of this equation mean?

A
30
Q

What happens when a dielectric is placed between the plates of a capacitor?

A

The individual molecules become polarised

31
Q

Do dielectric materials have different permitivities?

A

Yes - this is the ability for the dielectric to hold an electrical charge. This is shown by the letter E

32
Q

EMF definition

A

The amount of chemical energy converted to electrical energy per coulomb of charge (C) when passing through a power supply

equal to the terminal potential difference when no current flows.

33
Q

EMF Equation

A
34
Q

is EMF a force

A

It is not actually a force, and is measured in volts

35
Q

how is emf measured

A
36
Q

what is terminal potential difference

A

the potential difference across the terminals of a cell

If there was no internal resistance, the terminal p.d would be equal to the e.m.f

Since a cell has internal resistance, the terminal p.d is always lower than the e.m.f

37
Q

describe what lost volts are and why they exist

A
  • In a closed circuit, current flows through a cell and a potential difference develops across the internal resistance
  • Since resistance opposes current, this reduces the energy per unit charge (voltage) available to the rest of the external circuit
  • This difference is called the ‘lost volts’
  • Lost volts is usually represented by little v
38
Q

lost volts def

A

The work done per unit charge / coulomb to overcome the internal resistance / resistance inside the battery (when current flows)

39
Q

internal resistance def

A

The resistance of the materials within the battery

a level physics (33 decks)

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