Physics: Urgent Question !!!!! (1 Viewer)

[Exon]

Physics: Difficult (for me) Urgent Question !!!!!

I'm stuck on Physics... please help me!

The heating coil of an electric jug consists of 6m of a thin conductor. It develops 2400W when connected to 240V supply.

A) Calculate the power it would develop if used overseas in a 110V circuit

B) Comment on the efficiency of the jug

C) Calculate the current the jug would draw in Aust.

D) Calculate the current it would draw overseas with a 110V supply.


I've lost my Physics compass and can't find direction. THanks.

 

[Exon]

Re: Physics: Difficult (for me) Urgent Question !!!!!

lol please help!

 

[ajdlinux]

Re: Physics: Difficult (for me) Urgent Question !!!!!

A)

P = VI
2400 = 240 x I
I = 10 A

V = 110
P = 110 * 10
= 1100 W

 

[Exon]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Incorrect - answer is 504W - but how??

 

[ratcher0071]

Re: Physics: Difficult (for me) Urgent Question !!!!!

I'm stuck on Physics... please help me!

The heating coil of an electric jug consists of 6m of a thin conductor. It develops 2400W when connected to 240V supply.

A) Calculate the power it would develop if used overseas in a 110V circuit

B) Comment on the efficiency of the jug

C) Calculate the current the jug would draw in Aust.

D) Calculate the current it would draw overseas with a 110V supply.


I've lost my Physics compass and can't find direction. THanks.

A)
2400/x = 240/110
240x=2400 * 110
240x=264000
x=1100 Watts

C) Power (W)=Voltage(V) * Current (A)
2400=240 * A
A=10 amperes

D)
1100=110*A
A=10 amperes

 

[Exon]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Answers (BOB): a) 504W c) 10A d) 4.85A


How???

 

[ratcher0071]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Answers (BOB): a) 504W c) 10A d) 4.85A


How???

I also don't get why Question A) can be 504W. Because:
Power:Voltage is
2400:240
10:1

therefore
x:110
x=110 * 10
x=1100 watts

For Question C) let's assume Power = 504W
P=VI
504=110 * I
I = 4.58 amps

 

[Felix Jones]

Re: Physics: Difficult (for me) Urgent Question !!!!!

none of you used the fact that it's 6 cm long, that may solve your problem....but dunno how.

 

[ratcher0071]

Re: Physics: Difficult (for me) Urgent Question !!!!!

none of you used the fact that it's 6 cm long, that may solve your problem....but dunno how.

Its 6m not 6cm, plus it doesn't matter. All's i know is R is proportional to l

therefore resistance is 6 ohms

P=V² / R
P=110² / 6
P=12100/6
P=2016.67 Watts

wtf???

 

[Felix Jones]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Its 6m not 6cm, plus it doesn't matter. All's i know is R is proportional to l

therefore resistance is 6 ohms

P=V² / R
P=110² / 6
P=12100/6
P=2016.67 Watts

wtf???

ooh my bad (cm thing), but of course it matters, it's proportional therefore if you increase length then resistance will increase. besides why would they give you numerical information if you don't need it. obviously your ways didn't work so im just suggesting.

 

[ratcher0071]

Re: Physics: Difficult (for me) Urgent Question !!!!!

ooh my bad (cm thing), but of course it matters, it's proportional therefore if you increase length then resistance will increase. besides why would they give you numerical information if you don't need it. obviously your ways didn't work so im just suggesting.

Sometimes the question makers try to trick you into using all the data given, when you only need to use a few. Sneaky people!

 

[Felix Jones]

Re: Physics: Difficult (for me) Urgent Question !!!!!

yeah true, but previous methods didn't work, now im trying to find formulas that relate distance and power (no luck so far).

 

[Felix Jones]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Incorrect - answer is 504W - but how??

answer may be wrong, for it to be 504W, then current has to be 4.58A....where does that come from??

 

[Exon]

Re: Physics: Difficult (for me) Urgent Question !!!!!

Help!

 

[ajdlinux]

I suppose it's a non-ohmic resistor, therefore the resistance would change with current.

P1 = 2400W
V1 = 240V
I1 = 10A

V=IR
240=10*R
R = 24 ohms

110 = 24 * I
I = 4.58A

P = VI
P = 110 * 4.58
= 504 W