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gcse Physics > Electric Circuits > Flashcards

Electric Circuits Flashcards

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1
Q

What is the purpose of an electric circuit

A

To transfer energy from the power source to the components where it is converted into useful forms

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2
Q

Why must a circuit be complete

A

So that the charges are able to travel around the circuit and deliver energy

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3
Q

Current definition

A

The rate of flow of charge

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4
Q

What is the unit for for current and what apparatus do we use to measure current

A

Amps

Ammeter

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5
Q

Which circuit is current the same at all points of the circuit and why

A

Series circuit because the charges can only flow along one path

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6
Q

Why do parallel circuits have varying current

A

The charges can follow a choice of paths around the circuit
The current spots at a junction and rejoins at a junction do the current into a junction is the same as the current out of the junction

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7
Q

What is conventional current

A

Electrons flow from the positive terminal to the negative terminal because they didn’t know about electrons

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8
Q

Which way do electrons really flow through the circuit and why

A

Actually flow from the negative terminal to the positive terminal because the electrons which are negative repel against the negative terminal and are attracted to the positive terminal

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9
Q

Equation for current

A

Current = charge/ time

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10
Q

What equation links time, current and charge

A

Current = charge/ time

Time = charge / current

Charge = current x charge

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11
Q

Series circuit (4)

A

Only have one path

If a component breaks in the circuit the whole circuit turns off

Energy has to be split between each component so light bulbs are dim

Current stays the same though out the circuit

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12
Q

Parallel circuit (4)

A

Have lots of paths and branches

If a component breaks the circuit still works for the other components

All the energy from one electron can be given to each component, doesn’t need to share, so the bulb is brighter. Each branch receives the same amount of energy per coulomb

Current changes as electrons split off to different branches of the circuit

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13
Q

Advantages to series circuits (3)

A

Easy to construct

Less wiring to connect more components to the circuit

Whole circuit can be controlled by a switch

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14
Q

Disadvantages of series circuits (2)

A

Bulbs will be dimmer as energy is being shared

If one component breaks the whole circuit doesn’t work

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15
Q

Advantages of parallel circuits (3)

A

All the bulbs are brighter as the energy is not being shared

If a component breaks the rest of the circuit still works

Each component can be individually controlled

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16
Q

Disadvantages to parallel circuits (1)

A

Hard to construct if you want to add another component

17
Q

Voltage definition

A

A measure of how much energy is given to or taken away from a coulomb of charge as it passes around a circuit

18
Q

How is potential difference measured

A

Using a voltmeter

It is placed in parallel so that energy per coulomb before a component can be compared to after

19
Q

What other unit can potential difference be measured in

A

Joules per coulomb

This is because of the equation that links voltage, energy transferred and charge

20
Q

Equation for voltage

A

Voltage = energy transferred/ charge

21
Q

What equation links energy transferred, charge and potential difference

A

Potential difference = energy transferred/ charge

Energy transferred = potential difference x charge

Charge = energy transferred/ potential difference

22
Q

What is linked to current and voltage

A

resistance

23
Q

What is resistance

A

A measure of how difficult it is for a current to pass through a component. Resistance is measured in Ohms using an ohmmeter

24
Q

What is the the equation that links voltage, resistance and current

A

Voltage = resistance x current

25
Q

What is the relationship between current and voltage for a resistor

What would the graph look like

A

As voltage increases, current increases so they have a directly proportional relationship
So if voltage doubles then current doubles

V🐟I

Straight line with a positive correlation through the origin

26
Q

What happens to the current and voltage if a component has a higher resistance

A

There needs to be a higher voltage in order to have the same current pass through the component as it would be harder to get past it as it has a higher resistance

27
Q

Where does resistance come from

A

The electron carrying energy collide with the atoms in the component and lose some of their energy causing the atoms in the component to vibrate and heat up

28
Q

What is the relationship between voltage and current through a metal filament lamp

What would it look like on the graph

Why is this

A

Voltage and current are not directly proportional
The line is a curved shape on the graph through the origin

To get bigger currents, even larger voltages are needed as more energy is being transferred to heat energy in the lamp

29
Q

What is the relationship between voltage and current through a diode
What does the graph look like

A

As voltage increases current also increases however there needs to be high enough voltages to get current as resistance is very very high

Straight horizontal line so current is 0, then smooth curve upwards at higher voltages

30
Q

Why must voltages be high for current to pass through a diode

And say something about which way current has to flow in a diode

A

Coulombs of charge need a certain amount of energy to pass through a diode as there is very high resistance

The symbol tells us that current needs to flow the conventional way, this means that current can only flow one way through the diode

31
Q

Why do thermistors not behave like normal conductors

A

The resistance of a thermistor decreases as temperature increases as thermistors are made out of semiconductors

gcse Physics (11 decks)

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