Physics 2

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  • Created by: Lauren33
  • Created on: 16-11-15 16:46


  • Have a nucleus containing protons and neutrons

  • Electrons surround the nucleus

  • Atom has no overall charge


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Electrostatic charges

Electrostatic charges:

Insulating materials can be given an electrostatic charge by rubbing two materials together.

Electrons are transferred from one material to another.

The material that has gained electrons has a negative charge and the other a positive charge.

A charged object can attract uncharged objects, it induces a charge on the object.


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Uses and Dangers

Uses and Dangers

Electrons can move to cancel out a charge on you, maybe cause a ‘shock’. This is called earthing.

Lightning happens when a charge builds up in clouds.

Using static electricity:

Used in paint sprayers. Droplets all get the same kind of charge so they repel and spray evenly and attracts to the object of opposite charge.

A bonding line has to be used to earth any static charge on an aeroplane or truck before refuelling starts.

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Electric Currents

Electric Currents

 The size of a current is a measure of how much charge flows past a point each second, the rate of flow of charged particles.

Measured in coulombs(C).

One amp is one C of charge per second.

 Charge = current × time

 Q = I × T

 Key points:

  • Conductors are difficult to charge because the electrons can easily move through them

  • A flow of electrons is an electric current

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Current and Voltage

Current and Voltage

The current in a circuit is measured using an ammeter.

The voltage is measured using a voltmeter.

1 volt = 1 joule per coulomn

If the voltage is increased, the current increases, if it is decreased, the current decreases.

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Resistance, Current and voltage

Resistance, Current and voltage

Resistance is a way of measuring how hard it is for electricity to flow through it.

Measured in ohms(Ω).

 Higher the resistance, smaller the current.

 A resistors or variable resistors can change the resistance.


 Potential difference/voltage(volts) = current(amps) × resistance(ohms)

V = I × R

 Shorter wire = less resistance = more current = brighter bulb

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Transferring Energy

Transferring Energy


Power is the energy per second

Measured in Watts

1 Watt = 1 Joule per second

  • Electrical power(watt) = current(amp) × potential difference/voltage(volt)

    P = I × V 

    P = V2/R

    P= I2R

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Total energy transferred by an appliance depends on its power and how longs its switched on

  • Energy transferred(joule) = current(amp) × potential difference/voltage(volts) × time(seconds)

    E = I × V × t


    Must be converted to seconds.

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Vectors and Velocity and Velocity

Vectors have both size and direction.

Distance – path/route taken

  • Displacement  – distance in a straight line from start to finish


    Distance-time graphs:

  • Gradient = speed

  • Speed is always positive

  • Velocity can be positive or negative

    Velocity(m/s) =

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Velocity and Acceleration

Velocity and Acceleration


  • Is a change in velocity

  • Is a vector quantity


    Acceleration(m/s2) =


    a =

a = acceleration

v = final velocity

u = initial velocity

t = time taken



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Velocity-time graphs

Velocity-time graphs:

  • The area under the graph represents the distance travelled by the object


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Resultant Forces

Resultant Forces


If there is more than one force on something, all the forces can be combined into a resultant force.


Free-body diagrams:

  • Shows all the forces on something

  • Shows the direction

  • Larger forces shown using longer arrows

  • Used for forces on the same body


    Action and reaction forces:

  • Two touching objects exert force onto each other

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Forces and Acceleration

Forces and Acceleration


Acceleration depends on 2 things:

  • Mass of the object

  • Size of the force


    Force(N) = mass(kg) × acceleration(m/s2)

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Terminal Velocity

Terminal Velocity


Calculating weight:

  • The gravitational field strength on Earth is 10N

  • Mass must always be in kilograms


    Weight(N) = mass(kg) × gravitational field strength(N/kg)


    W = m × g


  • Mass – quantity of matter (doesn’t change)

  • Weight – measure of the pull of gravity on an object (can change)

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Terminal Velocity:

Terminal Velocity:

  • The force of gravity on a large mass is more than on a smaller mass

  • But the large mass also needs a greater force to accelerate it

  • The two affects cancel out

  • All masses fall at the same rate in a vacuum

  • The acceleration due to gravity on Earth is 10 m/s2

    Gravity has units of acceleration too. It is not a force, but acts on objects to cause downwards acceleration.

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