Physics

Physics

Static electricity
1. Caused by an electrostatic charge building up on an insulating material
2. All atoms contain electrically charged particles called electrons and protons
  1. Protons have positive charge, and are found in the nucleus
  2. Electrons move around the nucleus
  3. Noramlly atoms have no positive charge because the the +protons are balanced by the -electrons
  4. Neutrons have no charge
3. If you rub 2 insulating materials together, electrons maybe transferred, but protons cannot be transferred
  1. Like magnets <+ +> <- -> >+ -<
4. rubbing a balloon on your head is called charging by induction
  1. The charge is called induced charge
Uses and Dangers of Static Electricity
1. You can build up an electrostatic charge from chairs or carpets, then you get a shock when you touch metal
  1. You get this shock when electrons flow between you and the object
    1. Electrons move fromyou to the earth, this process is called earthing, and means you have been discharged
2. Static electricity can build can build up in clouds, then it makes huge sparks between the cloud and the ground
  1. We can see lightening because there are charged particles flowing through the air
  2. We can alos hear it because lightening makes sound waves called thunder
  3. Lightening can kill people and damge buildings
3. Static electricity can also build up when fuel flows througha pipe
  1. To prevent a spark they have a bonding line (metal wires), this discharges without any sparks
  2. Static electricity can also be used in insecticide/spray paint. it spreads more evenly.
Current and Voltage
1. The size of the current is measured with an ammeter
  1. Ammeter placed in series
2. Potential difference is measured with a voltmeter
  1. Voltmeter placed parallel with the component
  2. In order to change the size of current in a circuit, you change the potential difference (voltage)
    1. The higher the potential difference the bigger the current
  3. It measures the difference between the electrons going into the component and those coming out
3. Energy is measured in Joules Charge is measured in Coulombs
  1. 1 Volt= 1 Joule per Coulombs
Electric Currents
1. Insulating material can be given a charge of static electricity, because any charge transferred to the material cannot be conducted away.
2. All materials contain electrons
  1. Electrons in an insulating material cannot move around
    1. But in some metals, electrons are free to move around.
      1. If the electrons in a metal flow, there is an electric current
3. Batteries supply a direct current
  1. Generators produce an alternating current, this means electrons may change directions many times every second
4. Units of charge=coulombs (c)
  1. 1 amp is a flow of 1 coulomb of charge per second
    1. Q= I X T Charge=Current X Time
5. Units of current=Amperes (a)
Changing Resistances
1. The current flowing in a circuit depends on the potential difference of the supply, and on the resistance of the circuit
2. Resistance is a way of measuring how hard it is for electricity to flow
  1. Resistance is measured in ohms
  2. The resistance in the circuit depends on the resistance of the components in the circuit
3. The higher the total resistance, the smaller the current
4. Potential Difference= Current X Resistance V= I X R
5. Thermistors ()() Detect Heat
  1. LDR ** Light Dependent
  2. Diodes >> Conduct electricity in one direction
Velocity and Vectors
1. Quantities like displacement, velocity and force are all called vector quantities
2. Velocity tells you how quickly an object is moving and the direction it is going, it's is measured in m/s
3. Distance Time Graphs
  1. Horizontal line= Stationary
  2. Straight sloping line= Constant Speed
  3. The steeper the line= The faster it is
  4. Speed is calculated from the gradient of the line
    1. Choose 2 points on the line, join to make a triangle
      1. Minus the first distance from the second distance eg. 240m- 80m= 160m
        Divide eg. 160m/80s=2m/s
      2. minus the original time from the second time eg. 280s- 200s= 80s
Transferring Energy
1. When current flows through a resistor, energy is transferred and the resistor becomes warm
  1. This is useful in kitchen appliances eg. electric fires, kettles
  2. A similar thing happen with all components, eg. motor- electrical energy, turned into kinetic energy
  3. Fuses are fitted into plugs to prevent fires, from all the friction of energy being transferred through small wires.
2. Power = The Energy Transferred Every Second
3. Electrical Power= Current X Potential Difference W= I X V
4. Energy Transferred= Current X Potential Difference X Time J= I X V X S

Next up

Description

Resource summary

Similar

	Created by Alicia Tamlyn almost 11 years ago