A group of MYP students are investigating the use of fuse wire to limit electric current. Safety: This experiment involves the use of relatively large electric currents and exposed molten wire. Use appropriate safety equipment at all times, as indicated. Apparatus: Battery, wire, resistor, ammeter, fuse

Fuse wire is used in electric circuit to prevent:Electrical appliances and circuit from high currentthe insulatorUs from electric shockthe ammeter

Assertion:safety fuses are made up of materials having a low melting pointreason: safety fuses should be resistent to to electric current

Formulate a relationship between the current rating of the fuse wire in a circuit and the amount of current the circuit can carry.

fuse or a circuit breaker may be used to protect the circuit.One type of circuit breaker is a Residual Current Circuit Breaker (RCCB).(a) (i) Use the correct answer from the box to complete the sentence.earth live neutralA fuse is connected in the ........................................... wire.(1)(ii) Use the correct answer from the box to complete the sentence.are bigger are cheaper react fasterRCCBs are sometimes preferred to fuses because they........................................... .(1)(iii) RCCBs operate by detecting a difference in the current between two wires.Use the correct answer from the box to complete the sentence.earth and live earth and neutral live and neutralThe two wires are the .............................................................................. wires.(1)(b) An RCCB contains an iron rocker and a coil.A student investigated how the force of attraction, between a coil and an iron rocker,varies with the current in the coil.She supported a coil vertically and connected it in an electrical circuit, part of whichis shown in the figure below .

AimTo observe how a fuse worksEquipment• strands of steel wool• cork• two pins• power supply• connecting wires• 2.5 volt globeMethod1 Leaving the power pack turned off, construct the circuit inFigure 7.3.21.2 Gradually increase the power supply voltage from zero,stopping when the fuse melts or the voltage reaches 3 volts,whichever comes first.Questions1 State the voltage at which the fuse melted.2 Explain why a globe was included in the circuit.3 Describe the role of a fuse in a circuit.4 Propose ways in which this fuse could be modified to allowgreater current before melting.