Problems in circuits please help?

Question

1.) A 2.0mm copper wire has a resistance of 1.85 ohm per thousand feet.

a.)Calculate the power lost if the wire is 200 feet long carrying a curent of 10 amperes.

b.)What is the voltage difference between the two ends of the wire.

2.)The shunt field winding of a DC motor has a resistance of 230 ohms. Calculate the power loss when the voltage is 120 volts.

3.)A one ampere fuse has a resistance of 0.5 ohm. It will melt or 'blow" when the instantaneous current flowing through it is large enough to create a power loss of 5 watts. What is the value of the melting current?

4.)An earth "ground" at the base of the transmission line tower has a resistance of 2 ohms.

a.)if the lightning stroke of 20,000 amperes strikes the tower, what would be the power dissipated in the ground?

b.)What would be the voltage drop across the ground?

5.)A Dc motor draws a current of 50A at 230 volts. If 200 watts is dissipated in the form of heat in the motor, how much power is available for mechanical work.

Answer 1

E=I*R and P=E*I = I2*R =V2/R

1. a. P = I^2*R = 10^2 * (1.85*.2)     b. E = I*R = 10*)1.85*.2)

2. P = V^2/R

3. P = I^2 * R

  5J/s = I^2 * 0.5 Solve for I.

4.a P = I^2 * R = (20k)^2*2

b. V = I*R = 20k * 2

5. Net Power = Total Power - heat

Total Power = E*I = 50*230

subtract 200W to get net.