Electricity (Unit 2)

• An electric current is the flow of charge through a conductor. It is measured in amps (A)
• Current is measured in a circuit using an ammeter
• The size of electric current indicates the rate at which the charge flows
• One coloumb of charge is equal to charge carried by apporximately $6×10¹⁸$electrons
• Charge (Q, coulombs) = current(I, amps) * time, t(seconds)
• The ammeter is always connected in series to the circuit. The current through the ammeter is directly proportional to the current in the circuit.
• Potential difference across a component can be calculated as V=IR where R is resistance
• Voltage is measured with a voltmeter
• A voltmeter measures potential difference between two points in a circuit without affecting the flow of electricity.
• Ohms law states that voltage equals current multiplied by resistance
• Resistance is measured using an ohmmeter which has very high internal resistance so it does not affect the flow of electrons when measuring resistance
• If the Voltage across a circuit is equal to 1, the component is transferring 1 joule of energy each time 1 coloumb of charge passes though it.
• Energy Transferred, E(joules) = Charge, Q(coloumbs) * Voltage, V (volts) 


  E = Q*V
• A series circuit is a circuit with no branches or junctions and there is only on path the current can flow through.
• Parallel Circuits are circuits with more than one path for current to flow through.
• In a series circuit if you turn on the switch, all the bulbs will turn on.
• In a Series Circuit if one bulbs breaks, the whole circuit will stop working as there will be a gap in the circuit.
• In a Parallel circuit, Switches can be placed anywhere to switch each light bulbs on and off
• In a Parallel Circuit, if one bulb breaks on that branch will be affected, all the other branches and lighbulbs will still work.
• In a series Circuit the current is the same in all parts meaning that the current is not used up
• In a Parallel circuit the current is not the same in all parts of the circuit.
• Charge carriers in metals are electrons
• The reason why Metals are good conductors of electricity is because they have free electrons moving in them
• Thermistor is a resistor that changes resistance with temperature.
• Light Dependant resistors are resistors that decrease in resistance as light intensity increases.
• A diode is a one-way valve that allows current to flow in one direction only.
• A Light Emiting diode is a diode that emits light when current is flowing through it
• LED's are made from semiconductors
• LED's are made from semiconductors