physics/electricity

Anyone good at physics/electricity?


A certain appliance running at 240 V consumes 325 W of power. How much energy does it use in one hour?

The answer is in Joules


Power transmission lines often use a form of electric current called alternating current, but in many regions, such as the Province of Quebec, high-voltage direct-current lines are used instead. Direct current is the kind of electric current you are studying in this chapter. A certain direct-current power transmission line has a resistance of 0.255 Ω/km. 812 kV of potential drives the current from the generating station to a city located 125 km from the plant. What is the power loss due to resistance in the line?

The Answer is in Watts


and last but not least.....

A length of nichrome wire (composed of nickel and chromium) is 75.0 cm long and has a rectangular cross section measuring 0.700 mm by 0.500 mm. The resistivity of nichrome is 1.08×10−6 W×m. If a potential difference of 225 V is applied between the two ends of the wire, how much current flows through it?

Answer is in Amperes

72634.25 J

8351.02 W

2.438 A

how does i V=IR?

>>3
U=RI, damn it!
This annoys me almost as much as those damn engineers with their imaginary j's.

All signs point to 1.21 niggawatts.

>>4
actually J=sigma*E if you want to be really correct

"A certain appliance running at 240 V consumes 325 W of power. How much energy does it use in one hour?"
1 W = 1 J/S
325 J/s * 3600 s = 1170000 J

"A certain direct-current power transmission line has a resistance of 0.255 Ω/km. 812 kV of potential drives the current from the generating station to a city located 125 km from the plant. What is the power loss due to resistance in the line?"

P = IV, V = IR, I = V/R, P = V^2 / R

.255 Ohms/km * 125 km = 31.875 Ohms
v = 812 kV = 812000 V

P = 812000^2 / 31.875 = 2.06 * 10^10 W