If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.
You already know Dokkio is an AI-powered assistant to organize & manage your digital files & messages. Very soon, Dokkio will support Outlook as well as One Drive. Check it out today!
Comments (11)
johnlittlephysics said
at 10:47 pm on Jun 3, 2014
Wey Hsuan: I would just like to ask if a fuse blows, can current still flow through the fuse? will the current in the circuit be affected?
johnlittlephysics said
at 10:52 pm on Jun 3, 2014
Fuse blows means the wire melts and breaks, so no current can flow through it.
When a current reaches or exceeds the rating of a fuse (e.g. a fuse with rating 5 A, current flowing through it is greater or equal to 5.0 A),
we can say:
1. the fuse 'blows' and cuts off the current flow
OR a better version
2. the fuse melts and breaks the circuit, so current stops flowing through it.
johnlittlephysics said
at 5:23 pm on Jun 5, 2014
Celeste: What does it mean by "any damaged insulation between the live and neutral wires may result in a short circuit"? Also, why is this an electrical hazard?
johnlittlephysics said
at 5:42 pm on Jun 5, 2014
In a normal cable to an electrical appliance, the 3 wires with insulation are bundled together in a singe cable.
See http://www.rospa.com/homesafety/Images/NorthernIreland/electricity/garden9.gif
1. If the insulation of the live and neutral wires are damaged, current can flow between the wires, resulting in a short-circuit.
2. Without any resistance between the 2 wires, a large current flows, heats up the cable and may cause an electrical fire. Usually, this is prevented by a fuse (connected to live wire) which melts and breaks the circuit.
johnlittlephysics said
at 5:43 pm on Jun 5, 2014
2. A circuit breaker in the house may also trip to provide additional protection.
Goh Ying Ting said
at 11:31 am on Jun 17, 2014
Hi Mr Ang, could you explain textbook pg. 394 mcq qn 10 please? I think the answer is B but I'm not so sure. Thanks!:)
johnlittlephysics said
at 10:30 pm on Jun 17, 2014
I've reposted this question under "TYS/Textbook" - Electricity (also link from frontpage top menu)
http://nyghsec3physics.pbworks.com/w/page/79359794/tys_electricity#comment1403015379
Tessa Ng said
at 10:15 pm on Sep 2, 2014
Hi Mr Ang,
Do we use the equation "P=I^2R=V^2/R" when calculating the resistance of one particular element in the circuit that is connected in parallel and for calculating the total power dissipated? Thank you
johnlittlephysics said
at 10:21 pm on Sep 2, 2014
Yes. In fact P has 3 forms including P = VI, provided R is resistance of the element (component), I is current passing through it and V must be the p.d. across this component.
johnlittlephysics said
at 5:24 am on Sep 29, 2014
Celeste: What happens when the live wire accidentally touches the neutral wire?
johnlittlephysics said
at 5:24 am on Sep 29, 2014
Normally these wires are connected across a resistance (of the appliance), so the current is not high.
If the two wires touch each other, resistance between them is zero, so the current would be very large (just like connecting a copper wire across a 230V battery). Sparks may be seen. The very large current will heat up the wires rapidly, melting the insulation and may cause an electrical fire.
You don't have permission to comment on this page.