PHYSICS Electricity in the home CHAPTER 5 (P3- The electrical power…
PHYSICS Electricity in the home CHAPTER 5
P1- Direct current (d.c.) flows in one direction only. Alternating current (a.c.) repeatedly reverses it's direction of flow.
P3- The energy transferred to a device is ENERGY TRANSFERRED (joules) = POWER (watts) x TIME (seconds)
P1- To measure the frequency of an a.c. supply, measure the time period of the waves, then use the equation. FREQUENCY = 1 ÷ TIME TAKEN FOR 1 CYCLE.
P1- A mains circuit has a live wire, which is alternately positive and negative every cycle, and a neutral wire at zero volts.
P1- The peak potential difference of an a.c. supply is the maximum voltage measured from zero volts.
P2- Sockets and plug cases are made of stiff plastic materials that enclose the elctrical connections. Plastic is used because it is a good electrical insulator.
P2- A mains cable is made up of two or three insulated copper wires surrounded by an outer layer of flexible plastic material.
P3- The power supplied to a device is the energy transferred to it each second.
P4- The energy transferred to a component is ENERGY (joules) = POTENTIAL DIFFERENCE (volts) x CHARGE FLOW (coulombs).
P3- The electrical power supplied to an appliance is equal to POWER (watts) = CURRENT (amps) x POTENTIAL DIFFERENCE (volts)
P3- The correct rating (A) for a fuse: = electrical power (watts) ÷ potential difference (volts).
P2- In a three-pin plug or three-core cable, the live wire is brown, the neutral wire is blue, and the earth wire is striped green and yellow.
P2- The earth wire is connected to the longest pin in a plug and is used to earth the metal case of a mains appliance.
P4- When charge flows through a resistor, energy transferred to the resistor makes it hot.
P4- When charge flows around a circuit for a given time, the energy supplied by the battery is equal to the energy transferred to all the components in the circuit.
P4- The charge flow is CURRENT (amps) x TIME (seconds).
P5- The energy supplied to an appliance is .. ENERGY TRANSFERRED FROM THE MAINS (joules) = POWER (watts) x TIME (seconds).
P5- A domestic electricity meter measures how much energy is supplied.
P5- Useful energy used = efficiency x energy supplied.
CABELS AND PLUGS
ELECTRICAL POWER AND POTENTIAL DIFFERENCE
ELECTRICAL CURRENTS AND ENERGY TRANSFER
APPLIANCES AND EFFICIENCY