Physics Topic 3 - Electricity

• Electric potential difference (V) is measured in volts (V). It is also known as voltage or EMF.
• What is current?

  Current is the rate of flow of charge
• What unit is current measured in

  Amps
• What is potential difference ?

  The energy transferred per unit charge
• What is potential difference measured in?

  Volts
• What sources are required for a flow to charge?


  -Closed cirquit

  -Source of potential difference (bulb)
• Equation for the calculation of current

  Current = Charge divided by time
• What happens when conductors are rubbed together ?

  -Electrons flow in and out of conductor (cancel other effects

  -Remain neutral
• When does sparking occur and what happens to the charges


  Sparking occurs when enough charge is build up and two objects are close but not touching

  The charge jumps from a highly negative to a highly positive object to balance them out
• Properties of insulators


  -Dont consuct elecricity

  -Particles cant flow through object

  -Particles are fixed
• Properties of conductors


  -Conduct electricity

  -Particles are delocalised

  -Particles flow
• What is charge?


  -Charge is a property of all matter

  -Can be positive or negative

  -If a body has the same amount of positive and negative charge they cancel out
• Why do two insulators being rubbed together become charged

  Because the particles cant flow
• What happens to the charge of insulators when rubbed together?


  -The insulators losing electrons become positive

  -Gaining electro becomes negative
• What happens when two insulators are rubbed together

  Electrons are transferred from one to the other
• What force is on electrostatic force

  Non contact
• What is the voltmeter measuring potential difference connected in?

  In parallel across the component
• What is the ammeter measuring current connected in?

  Series
• What is the equation for energy transferred?


  Engert transferred (J) = Charge x time
• What is the equation for resistance, current and voltage?

  Voltage (V) = Current (A) x Resistance
• What is ohms law?

  Resistance is constant or current is directly proportional to voltage
• Equation for power


  Power = Current x Voltage