IGCSE Coordinated Science: Current, Electromotive forces and Potential Difference Current, Electromotive forces and Potential Difference 1. State that current is related to the flow of charge Current: is the flow of electrical charge within the circuit. 2. Demonstrate understanding that a current is a rate of flow ofcharge and recall and use the equation: I = Q/t More specifically, current is the rate of flow of charge in a given point of a circuit , measured in ampere , or amp (A). The general equation for working out current when you have steady flowof charge is: I = Q/t ● I = Current measured in amps ● Q = the charge carried measured in coulombs ● t = Time 1 Amp is equivalent to 1 coulomb of charge flowing through a fixed pointper second. Amps = coulombs / seconds 3. Use the term potential difference (p.d.) to describe what drivesthe current between two points in a circuit. The potential in an electric circuit is a measure of how much joules per coulomb (Volts) there are in a specific point of a circuit. To move an electric current through a metal wire, it takes work/energy. Ifyou think about it, when you run electricity through a wire, it gets HOT.The electric potential energy carried by the current is used to push thecurrent through the wire and the energy is lost as heat.
Therefore, potential represents how much energy there is to drive a current through the wire and is measured in volts (v) . The potential difference is the difference in potential between two points of a circuit. It represents how much energy is given off when going through aspecific point as it moves from a higher potential energy to a lowerpotential energy. For example, if the potential difference of a light bulb is 3v, it means that3 joules of electric potential energy that each of coulomb is being lost asheat and light energy as it moves through the light bulb. In any electrical circuit, the potential at the end of the circuit is always 0 i.e. a potential of 0 volts. 4. Distinguish between the direction of flow of electrons andconventional current Normally, in a electrical circuit, the flow of electrons go from (-) pole ofthe battery to the (+) pole. However, the conventional current flows in the opposite direction of theflow of electron. This is because the battery provides an electro-motive force (e.m.f) that pushes the electrons forward, making them do work.
5. Demonstrate understanding that e.m.f. is defined in terms ofenergy supplied by a source in driving charge round a completecircuit Electro-motive force (e.m.f) is the voltage (potential) that a battery will supply. It is the driving force that gives the electrons the energy to movearound the circuit. For example, a 12V battery will provide a e.m.f of 12V.