Electricity

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Physics Ebbin Binny

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Electricity Electricity Presentation Transcript

  • Electricity Part I – Circuits
  • People Benjamin Franklin Thomas Edison  Have you heard of these people?  Why are they important?
  •  Benjamin Franklin Proved that lightning was electricity by flying a kite in a lightning storm Helped people understand the principles of electricity • Thomas Edison – Invented the electrical light bulb
  • What is electricity?  Electricity is a form of energy  It is caused by a flow of tiny particles called electrons through a material
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire.
  • Electricity Electricity is a flow of electric charges along a wire. This flow of electric charge is called a current. Current is measured in the units of Amps (A).
  • What is an Electrical Circuit?  A circuit is an electrical device that provides a path for electricity to flow
  • Complete or Incomplete?  A complete circuit is where all the components of a circuit are joined up and there are no gaps  The pathway for electricity is complete
  • Complete or Incomplete?  An incomplete circuit is where the pathway for electricity is broken  The electricity cannot flow
  • Circuit Diagrams cell switchlamp wires
  • Component Symbols – a cell  The cell stores chemical energy and transfers it to electrical energy when a circuit is connected.  The long line is the positive end  The short line is the negative end
  • Battery  When two or more cells are connected together we call this a Battery.  The cells chemical energy is used up pushing a current round a circuit.  It is important that each cell faces the right way
  • Switch  A switch can be open (as shown) or closed  When the switch is open, the circuit is incomplete – no electricity can flow  What happens when the switch is closed?
  • Bulb / Lamp  The lamp lights up when electricity flows through it  What would happen to a lamp if there was an open switch in the circuit?
  • Wires The wires which carry electricity consist of two parts: • The metal wires (conductor). • The plastic coating around the metal wires (insulator). • Prevents people from being electrocuted. wires
  • Voltmeter  The voltmeter measures the voltage of the circuit  We will discuss this in another lesson
  • Ammeter  The ammeter measures the current in the circuit  We will discuss this in another lesson
  • Resistor  A resistor can change the amount of current in a circuit  In a variable resistor, the resistance can be changed.
  • Resistance
  • Variable resistors Look at Figure 17.6 on page 207. Path of current flow Terminal A  metal bar  sliding contact  coils of wire  Terminal B
  • Variable resistors Look at Figure 17.6 on page 207. The sliding contact can be adjusted so that the current passes through only a few coils of wire or many coils of wire. If the sliding contact is near Terminal A : current passes through many coils of wire = high resistance If the sliding contact is near Terminal B: current passes through a few coils of wire = low resistance
  • Variable resistors Turn the dial here for low resistance higher resistance
  • Fuse  A fuse is a safety device  When the current is too high, the fuse breaks Example The wire inside a 3A fuse will melt when the current is greater than 3A.
  • Motor  A motor can be fitted into a circuit  What do you think happens to a motor in a complete circuit?
  • Circuit Symbols Voltmeter Ammeter Variable Resistor Switch Bulb Motor Cell Battery
  • types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
  • The components are connected end-to-end, one after the other. They make a simple loop for the current to flow round. SERIES CIRCUITS If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
  • PARALLEL CIRCUITS The current has a choice of routes (paths). The components are connected side by side. If one bulb ‘blows’ there would still be a complete circuit to the other bulb so it stays lit.
  • measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
  • measuring current A A This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT
  • measuring current SERIES CIRCUIT PARALLEL CIRCUIT • current is the same at all points in the circuit. 6A 6A 6A • current is shared between the components 4A4A 3A 1A
  • copy the following circuits and fill in the missing ammeter readings. ? ? 4A 4A 4A 3A? ? 1A ? 3A 1A 1A
  • measuring voltage The ‘electrical push’ which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeter V
  • Different cells produce different voltages. The bigger the voltage supplied by the cell, the bigger the current (the cell gives a bigger push to the electrons). measuring voltage
  • measuring voltage Unlike an ammeter a voltmeter is connected across the components (in parallel) Scientist usually use the term Potential Difference (pd) when they talk about voltage.
  • Final GPE Initial GPE Potential Difference
  • pd
  • measuring voltage V This is how we draw a voltmeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT V
  • V measuring voltage V V V
  • series circuit 1.5V • voltage is shared between the components 1.5V 3V
  • • voltage is the same in all parts of the circuit. 3V parallel circuit 3V 3V
  • measuring current & voltage V V 6V 4A A A a)
  • measuring current & voltage V V 6V 4A A A A b)
  • answers 3V 3V 6V 4A 4A 6V 6V 6V 4A 4A 2A 2A 4A a) b)