Electricity

Power The electric power, P is defined as the rates of energy that supply to the circuit ( or the rates of work been done ) by sources of electric. The unit of electric power is the watt (W). One watt of power equals the work done in one second by one volt of potential … Read more

Electrical Energy From the definition of potential difference, the electrical work done is given by the equation W=QVWhereW = workQ = chargeV = potential difference Since the work done must be equal to the energy to do the work, therefore we can also say that the electrical energy ( E ) is also given by … Read more

Measuring e.m.f. and Internal Resistance Three methods can be used to measure the e.m.f. and internal resistance. Open circuit-Close circuit Simultaneous equation Linear Graph Open Circuit – Closed Circuit Open CircuitIn open circuit ( when the switch is off), the voltmeter shows the reading of the e.m.f.Close CircuitIn close circuit ( when the switch is … Read more

Internal Resistance The internal resistance of a source (cell or generator) is the resistance against the moving charge in the source. Load Resistance The load resistance in a circuit is the effective resistance against the moving charge outside the source of electric. Terminal Potential Difference The terminal potential difference or terminal voltage is the potential … Read more

Electromotive Force Potential Difference Similarities:Have same unit (Volt)Can be measured by Voltmeter DefinitionThe electromotive force (e.m.f.) is defined as the energy per unit charge that is converted from chemical, mechanical, or other forms of energy into electrical energy in a battery or dynamo. DefinitionThe potential difference (p.d.) between two points is defined as the energy … Read more

Electromotive Force In a circuit, the electromotive force is the energy per unit charge converted from the other forms of energy into electrical energy to move the charge across the whole circuit. In equation,where E = e.m.f.,W = energy converted from non-electrical forms to electrical formQ = positive charge. The unit of e.m.f. is JC-1 … Read more

Finding Potential Difference in a Series Circuit In the circuit above, if the current in the circuit is I, then the potential difference across each of the resistor is Example Find the potential difference across each of the resistors in the diagram above. Answer:The potential difference across the 2 resistors, V = 12VThe equivalent resistance … Read more

Finding Current in a Parallel Circuit In parallel circuit, the potential difference (V) across each of the resistors is equal to the e.m.f. (E) if the internal resistance of the cell is ignored. By Ohm’s Law Example 1: For the diagram above,a. find the reading of the ammeter.b. find the current in each of the resistors. Answer:a.Effective … Read more

Finding Current in a Series Circuit In a series circuit, the current flow through each of the resistor is equal to the current flows through the whole circuit. Potential difference (V) across the whole circuit is equal to the e.m.f. (E) if the internal resistance is ignored. Effective resistance for the whole circuit = R1 … Read more

Series Circuit The sum of the potential difference across individual resistor in between 2 points in a series circuit is equal to the potential difference across the two points. V = V1 + V2 Example Parallel Circuit The potential difference across all resistors in a parallel circuit is the same. V = V1 = V2 … Read more