Calculating Energy and Power in an Inductive Circuit

[lcam2]

Homework Statement

In a circuit composed of a battery a resistor and an inductor, the EMF from the battery is 12 V and the resistor has a resistance is 7.4 Ω. The inductor consists of a long, thin cylindrical coil of wire with 20000 turns, a radius of 5 cm and a length of 61 cm.

Answer the following questions for a time 1.2 seconds after the battery has been connected.


(a) What is the inductance of the solenoid?
(b) What is the current through the battery?
(c) How much energy has been delivered by the battery up to this point?
(d) How much of that energy is stored in the magnetic field of the inductor?
(e) How much of that energy was dissipated by the resistor?
(f) What is the energy density of the magnetic field in the solenoid?
(g) What is the strength of the magnetic field near the center of the coil?

Homework Equations

Inductance of a Solenoid
L=N^2*A*$$\mu$$/l

Area circle A=$$\pi$$R^2

Time constant
$$\tau$$=L/R

Energy stored on a magnetic field
U=(1/2) Li^2

The Attempt at a Solution

In part (a) i used the Inductance of a solenoid
(b) I used Time constant equation and i=$$\epsilon$$/r(1-e^(-t/$$\tau$$)

(c) for part c i was trying to use
P= i^2*V but i didnt' work.
the problem states
HELP: How do you calculate the power produced by a battery from its current and EMF? This will give you the energy per unit time produced by the battery.
HELP: How are power, time, and energy related? (Yes, you're going to have to do an integral.)

Thanks in advance!

 

[lcam2]

Is someone Willing to help me??

 

[cupid.callin]

Hi lcam2

Work done by battery is defined as qE
where q is charge delivered by battery and E is EMF

now for power, P = dW/dt = iE

Now sure but give it a try