Electrical Circuits

Charge is a property of matter that can cause a force if it nears another charge. There is two types of charge, positive and negative. 

• One rule to rememeber about charge is that opposites attract. Meaning two negative or positive charge will repel each other, but one negative and one positive will attract (like two magnets with north and south.)
• Charge is measure in coulombs - the symbol C.
• Protons carry a postitie charge, while Electrons carry a negative charge.
• Ammeters measure the amount of charge flowwing through a circuit. 
• A current of 1 ampere flowing is the same (=) as 1 coulomb of charge flowing through a circuit per second. So in other words, the size of the electrical current is the rate of flow of electrical charge.

Charge flow (C) = currrent (A) X time(S)

Q = I X t

Electical current is the flow of electons through a circuit.

• When current flows through a circuit, electrical work is done and energy is transferred.
• The current flowing through a circuit is measured in Amperes or Amps - and is measured by an Ammeter.
• In order to meausure the current through a component, the ammeter must be in series (a circuit where one component follows directly from another) which is shown below.

Potentail difference - or voltage, is the measure of the energy given to the charge carriers in a circuit. 

• Potential difference is measured in volts (V)
• The potential difference must be measures while a circuit is in parallel (a circuit where the current divides into two or more paths before recombining to complete the circuit.)

Potential Difference (V) = Energy (J) ÷ Charge (C)

V = E/Q

OR

Potential difference (V) = Current (A) X Resistance (Ω)

V = I X R

Resistance is the oppostition to current flow in a circuit. 

• Resistance is meausred in ohms - symbolised by the Greek letter omega (Ω)
• Conductors have low resistance, and insualtors have a high resistance.
• The resistance can be found by measuring the electric currrent flowing and the potential difference.

Resistance = potentail difference (V) ÷ Current (A)

R = V ÷ I

Power is the energy transferred each second - measured in watts (W)

Power (W) = current (A) X potential difference (V)

P = I X v

• The efficient transmission of power:
  • Energy can be transferred by an electrical current; any electrical appliance needs to be given enough energy every second. Electrical power can be delivered as a low current with a high voltage or a high current with a low voltage.
  • power = current² X resistance
    
  • The equation shows that a high current will have a much higher heating effect on the transmission wires than a low current. For this reason, transmitting energy at a high voltage with a low current will keep the wires cooler and waste less energy.