 # + - + + + + The world is filled with electrical charges: + + + + + - - - - - - - - -

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+ - + + + + The world is filled with electrical charges: + + + + + - - - - - - - - -

What is this electrical potential called? Static Electricity Static Electricity -- - - - - - + + + + +

Static Electricity The build up of an electric charge on the surface of an object. The build up of an electric charge on the surface of an object. The charge builds up but does not flow. The charge builds up but does not flow. Static electricity is potential energy. It does not move. It is stored. Static electricity is potential energy. It does not move. It is stored.

Van de Graaff generator Produces static electricity Produces static electricity Electrons are carried up a rubber belt & are transferred to the metal sphere Electrons are carried up a rubber belt & are transferred to the metal sphere The charge built up on the sphere is enough to send a spark several meters through the air. The charge built up on the sphere is enough to send a spark several meters through the air.

Static Discharge… Occurs when there is a loss of static electricity due to three possible things: Occurs when there is a loss of static electricity due to three possible things: Friction - rubbing Friction - rubbing Conduction – direct contact Conduction – direct contact Induction – through an electrical field (not direct contact) Induction – through an electrical field (not direct contact)

electric current continuous flow of electric charges through a material continuous flow of electric charges through a material unit=amp unit=amp

Electricity that moves… Current: The flow of electrons from one place to another. Current: The flow of electrons from one place to another. Measured in amperes (amps) Measured in amperes (amps) Kinetic energy Kinetic energy

How can we control currents? With circuits. With circuits. Circuit: is a path for the flow of electrons. We use wires. Circuit: is a path for the flow of electrons. We use wires.

electric circuit complete, unbroken path through which electric charges can flow complete, unbroken path through which electric charges can flow

There are 2 types of currents: Direct Current (DC) – Where electrons flow in the same direction in a wire. Direct Current (DC) – Where electrons flow in the same direction in a wire.

There are 2 types of currents: Alternating Current (AC) – electrons flow in different directions in a wire Alternating Current (AC) – electrons flow in different directions in a wire

simple circuits Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires

simple circuits When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.

circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;

circuit diagrams In circuit diagrams components are represented by the following symbols; batteryswitch motorammetervoltmeter resistor

types of circuit There are two types of electrical circuits; SERIES CIRCUITSPARALLEL 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. The components are connected side by side. If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.

measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A

measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A

measuring current SERIES CIRCUIT PARALLEL CIRCUIT current is the same at all points in the circuit. 2A current is shared between the components 2A 1A

Conductors vs. Insulators Conductors – material through which electric current flows easily. Conductors – material through which electric current flows easily. electrons are only loosely bound to their atoms electrons are only loosely bound to their atoms Insulators – materials through which electric current cannot move. Insulators – materials through which electric current cannot move. electrons are bound tightly to their atoms electrons are bound tightly to their atoms

Examples Conductors: Conductors: Metal Metal Water Water Insulators: Insulators: Styrofoam Rubber Plastic Paper

What is Resistance? The opposition to the flow of an electric current, producing heat. The opposition to the flow of an electric current, producing heat. The greater the resistance, the less current gets through. The greater the resistance, the less current gets through. Good conductors have low resistance. Good conductors have low resistance. Measured in ohms. Measured in ohms.

What Influences Resistance? Material of wire – aluminum and copper have low resistance Material of wire – aluminum and copper have low resistance Thickness – the thicker the wire the lower the resistance Thickness – the thicker the wire the lower the resistance Length – shorter wire has lower resistance Length – shorter wire has lower resistance Temperature – lower temperature has lower resistance Temperature – lower temperature has lower resistance

Factors that determine resistance of a wire Material wire is made of Length of Wire Diameter of wire Temperature of wire

What is Voltage or Potential Difference? The measure of energy given to the charge flowing in a circuit. The measure of energy given to the charge flowing in a circuit. 1. Difference in electrical potential between 2 places 2. Causes current to flow through electric circuit 3. unit = volt

The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.

WHAT IS VOLTAGE? Voltage is potential difference measured by a ______________ ? VOLTMETER The unit of measure in potential difference is called the volt. For that reason, potential difference may be called voltage.

Amperage The flow of electrons is measured in units called amperes. The flow of electrons is measured in units called amperes. The term amps is often used for short. The term amps is often used for short. An ammeter is this instrument and it is used to indicate how many amps of current are flowing in an electrical circuit. An ammeter is this instrument and it is used to indicate how many amps of current are flowing in an electrical circuit.

Difference between Volts and Amps Example – you could say that… Example – you could say that… Amps measure how much water comes out of a hose. Amps measure how much water comes out of a hose. Volts measure how hard the water comes out of a hose. Volts measure how hard the water comes out of a hose.

Ohm’s Law Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. Resistance = Voltage / Current Resistance = Voltage / Current Ohms = Volts / Amps Ohms = Volts / Amps

Practice with Ohm’s Law OhmsVoltsAmps 410025 1515010 23015 9455 6488

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