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Eddie's GCSE Physics > Electrical quantities > Flashcards

Electrical quantities Flashcards

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1
Q

Two types of electrical charge

A

positive and negative

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2
Q

What happens when two meet

A

opposite attract

Like charges repel

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3
Q

Unit of charge

A

Coulombs (C)

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4
Q

Explain field patterns of charges

A

Electric charges create electric fields in the regions around them

The electric field is the region in which another charge will experience a force

Field lines go away from positive charges and towards negative charges

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5
Q

What is an electron

A

A negatively charged particle

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6
Q

Definition - conductor

A

a material that allows charge to flow through it

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7
Q

Definition - insulator

A

a material that does not allow the flow of charge through it

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8
Q

Examples of conductors

A

metals

graphite

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9
Q

Examples of insulators

A

plastics

glass

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10
Q

Explain - charging by induction

A

When a charged object is held close to a conductor, electrons in the conductor are able to move towards or away from the charged object

e.g. if electrons from a piece of aluminium foil are attracted to a +ve charged rod

This causes the top of the foil to become -ve charged whilst the bottom edge of it will be left with a positive charge

The attraction between the positive rod and the -ve charges on the top surface of the foil will cause the foil to be attracted to the rod

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11
Q

When does the flow of current occur

A

When two oppositely charged conductors are connected together

This is called an electric circuit

The greater the flow of charge, the greater the electric current

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12
Q

Equation of charge (current and time)

A 
Q = IT
Charge = current x time
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13
Q

How to measure current

A

Using an ammeter

Ammeters must be connected in series

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14
Q

How is current caused in metals

A

by a flow of free, delocalised electrons

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15
Q

Explain - conventional current

A

the flow of electrons from negative to positive (even though electrons go the other way

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16
Q

What is electromotive force

A

The name given to the potential difference of the power source in a circuit

The Electromotive force is measured in volts (V)

17
Q

EMF of a power supply measured in volts is…

A

The amount of energy measured in joules supplied to each coulomb

18
Q

Explain - Potential difference

A

As charge flows around a circuit, energy is transferred to or from the charge

The P.D. between two points in a circuit is related to the amount of energy transferred between those points in the circuit

P.D. is measured in volts (V)

19
Q

1 volt is equal to

A

1 joule per coulomb (J/c)

20
Q

How to measure potential difference

A

Using a voltmeter

It must be connected in parallel with the part if the circuit being measured

21
Q

What is resistance

A

The opposition to current

The greater the resistance the lower the current

22
Q

What is the unit of resistance

A

Ohm

23
Q

Equation of resistance

A

R=V/I

24
Q

Factors affecting resistance of a wire

A

The longer the wire = greater resistance - the electrons will collide with more ions creating greater resistance

The thicker the wire = smaller resistance - the more space there is for the electrons so more electrons can flow

25
Q

What happens to resistance if the length is doubled

A

the resistance is doubled

The resistance of a wire is proportional to its length

26
Q

What happens to resistance if the cross-sectional area is doubled

A

Resistance is halved

The resistance of a wire is inversely proportional to its cross sectional area

27
Q

Describe the IV graph for a reistor

A

The current is proportional to voltage

28
Q

Describe the IV graph for a filament lamp

A

The current increases at a proportionally slower rate than the potential difference

this is because -

The current causes the filament in the lamp to heat up
As the filament gets hot its resistance increases
This opposes the current, causing it to increase at a slower rate

29
Q

What happens as electricity is passed around the circuit

A

Energy is transferred from power source to various components

In the components it loses energy in light, heat energy

30
Q

Equation connecting energy transferred current time and potential difference

A

E = IVT

Energy transferred = Current x Voltage x Time

31
Q

Equation for electrical power (watts)

A 
P = IV
Power = Current x time

Eddie's GCSE Physics (11 decks)

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