physics - effects of an electric currentand domestic circuit

describe an experiment that demonstrtes the heating effect of an electric current

list the factors that affect the heat produced in a current carrying conductor

the size of the current I; the resistance R of the conductor through which it flows; the time t for which it flows

state joules law

joules law states that the rate at which heat is produced in a conductor is directly proportional to the square of the current provided the resistance is constant

energy generating companies transmit electricity over large distances at high voltages

explain why high voltage is used

the heat produced is directly proportional to the current squared .therefore the smaller the current the less heat energy wasted in the wire per second. high voltage is used to minimize power loss

in a 3 pin plug what are each colour wire connected to

brown is connected to the live

blue is connected to the neutral

green yellow is connected to the earth

give one safety precaution when wiring a plug

ensure the correct colour wire is connected to the correct terminal

which wire contains the fuse

the live wire/brown

how does the fuse operate

a fuse is connected in the live part of a circuit. it consists of a thin piece of wire. current flows through the wire and it heats up.if the current exceeds the fuse’s rating the wire melts, breaks the circuit and disconnects it from the live

explain why using a fuse with too high a rating is dangerous

the fuse will not melt and a very large current could flow if a fault occured. this could cause a fire or increase the risk of electrocution

name a device found inn modern domestic circuits that has the same function as a fuse

a miniture circuit breaker

what is the purpose of a miniture circuit breaker

a mcb is a safety device that breaks a circuit if too largea current flows. it thus protects the equipment and the people using it .it has the same function as a fuse

what is the advantage of a mcb over a fuse

it operates faster than a fuse and can be reset after the fault is located

what is the function of the residual current device

it is a safety device that disconnects a circuit from the mains and prevents electrocution

when will a residual current device diconnect a circuit

when there is a difference in the value of the current flowing in the live wire and the neutral wire , it disconnects the circuit from the mains

an residual current device is rated at 30mA . explian the significance of this rating

the RCD disconnects from the mains if the value of the current in the live wire and the neutral wire differ by more than 30mA

give one advantage of an Residual current device over a miniature circuit breaker

an RCD res ponds much more quickly, and RCD responds to very small currents

why are some appliance not earthed?

because all external parts of the appliance are elecctrical insulatore and there is no risk of electrocution

what is a radial circuit

an appliance that takes a large current has a seperate live and neutral wire coming to it from the distribution box. the live wire has a fuse or MCB in it. such a circuit is called a radial circuit

define the kilowatt-hour

one kilowatt-hour is the amount of energy used by a 1000W appliance in one hour

whats another name for the chemical effect of an electric current

electrolysis

what is an ion

an atom or molecule hat has lost or gained one or more electrons

what are the charge carrier when and electric current passes through an electrolyte

in an electrolyte the charge carriers are positive and negative ions

name the unit of electrical energy used un the delivery of electricity to homes abd businesses

the kilowatt-hour

what are the charge carriers when an electric current passes through a metal or a filament bulb

electrons

what is the chemical effect of an electric current

this is when an electric current passes through a liquid and causes a chemical reaction in the liquid