Yr10 Electricity

8/6/2019 Yr10 Electricity

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Electricity


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Electricity

StaticIs stationary

E.g. Brush your hairWool socks in

tumble drier

CurrentFlows around circuit

E.g. turn on light

Walkman

Electricity occurs in 2 different forms


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Current Electricity

Electrons flow through a conductor

Negative to positive

Circuit = continuous loop for electronsto flow

Needs energy supply

Energy user


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Electrical components

Wire

Ammeter

Battery

Fuse

Connectedwires

Bulb

SwitchVoltmeter

Resistor

Rheostat


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Electrical symbols

Ammeter FuseConnected

wireBulb

ResistorWire

Rheostat

Battery

Voltmeter Switch


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CIRCUIT TYPESThe simplest type of circuit involves same current flowing

throughout the circuit.

This is called a Series circuit.

The path the electrons travel is as

shown.

The other main type of circuit has two

or more branches.

This is called a Parallel circuit.

The flow of electron is as shown.


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Series circuit

Has a single loop for electrons to travelround

Components are connected one afteranother

Current has to travel through all

componentsCurrent is the same at all points

Voltage is shared between components


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What are electric circuits?

Circuits typically contain a voltage source, a wire

conductor, and one or more devices which use theelectrical energy.

What is aseries circuit?

A series circuit is one which provides a single pathwayfor the current to flow. If the circuit breaks, all devicesusing the circuit will fail.


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Parallel circuit

Has two or more paths for electronsto flow down

Current is shared between thebranches

Sum of the current in each branch =total current

Voltage loss is the same across allcomponents


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What is a parallel circuit?

A parallel circuit has multiple pathways for the current to

flow. If the circuit is broken the current may pass through

other pathways and other devices will continue to work.


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Electricity

Electricity is forced around a circuit by

an electrical force field

Flow of electricity around a circuit iscalled CURRENT (I)

Current measured in amps (A)

Voltage (V) Increase or decrease inthe amount of electrical energy carried

by the current.


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Current (I)

Current is the flow of electrons

around a circuit

DC = direct current like batteryElectrons flow in one direction

AC = Alternating current like mains

Electron flow changes direction 50xper second


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Ammeter

Measures CURRENT(I)

Unit = Amp (A)

Current is flow of electronsConnect in series at the point you

wish to measure

RED to RED and BLACK to BLACK


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3 pin plug

3 wires

P = phase (brown or red)

N = neutral (blue or black)E = earth (yellow/green or green)


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Voltage (V)

Gain or loss of energy as it

passes through a component

Voltage lost = voltage gainedIn series voltage loss is shared

between components

In parallel voltage loss is the sameacross all components


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Voltmeter

Measures voltage

Unit = Volt (V)

Voltage increases as it passesthrough energy suppliers

Voltage is decreased as it passesthrough users

Connect in parallel around acomponent


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SUMMARY

In Series In Parallel

Current

Voltage

Always the same The branches share

electrons and add to the total

Voltage from source =

voltage used

Voltage is shared

between power users

Voltage is the same in allbranches


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Resistance (R)

The amount that a component

slows the current

As the electrons are slowed by a resistor, energy is

lost in the form of heat.

This means that current, resistance and voltage must

be linked.

This is Ohms law

The unit of resistance is the ohm, symbol ;V

I R


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OHMS Law

At a constant temperature the

potential difference in a circuit is

directly proportional to electric

current

V I


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Heating effect of electric current

Temperature is a measure of the

average kinetic energy of the

particles. Degrees Celsius ( C )

Heat energy is a measure of the total

kinetic energy of all the particles

making up an object.

joules ( J ) or kilojoules


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Effects of Heating

Temperature Rise

Expansion

Change of State


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Factors on which heating effect

depends:

H I (Square of the current)

H R (Resistance)H t (Time)

Combining all the factors:

H=IRt


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Power

Energy used by component per secondUnit of power is the Watt, symbol is W

One watt means that 1 joule of electrical energy is

being used up per second.

Current, voltage and power

are linkedP

I V


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How is electrical energydetermined?

Electrical energy is a measure of the amount of power

used and the time of use.

Electrical energy is the product of the power and the

time.

Example problem:

E = P X time

P = I V

P = (2A) (120 V) = 240 W

E = (240 W) (4 h) = 960Wh = 0.96 kWh


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