How Do You Solve Capacitor and Circuit Homework Problems?

[Nick L]

Ok, I have 2 homework problems that I don't really know where to even start.
The first one is:
A homemade capacitor is assembled by placing two 15-cm pie tins 20 cm apart and connecting them to opposite terminals of a battery. Calculate the following:
a) the capacitance
b) the charge on each plate
c) the electric field halfway between the plates
d) the work done by the battery to charge the plates

I was able to get part a, but I don't know where to begin for parts b,c, and d.


The second problem uses Kirchhoff's Rules.
Find the current in each of the three resistors of the circuit below:

I did not have any idea where to start with this one. I believe it has something to do with loops.

Any help on either of this would really be appreciated.

 

[Mentz114]

Nick, you should show the work you've done with the formulae you've got.
Questions b), c) and d) are all straightforward if you look up the formulae.

The current question needs Kirchoff's rules as you know - so why not look up these rules in a book or in Wiki ...

 

[m2003]

Hello,

I can help you with your capacitor and circuit problems. Let's start with the first one:

a) To calculate the capacitance, we can use the formula C = Q/V, where C is the capacitance, Q is the charge, and V is the voltage. In this case, the voltage is the same as the battery voltage, so we can use the value of the battery to calculate the capacitance. The formula becomes C = Q/E, where E is the electric field between the plates. So, for this problem, the capacitance would be the same as the battery voltage (in volts) divided by the distance between the plates (in meters).

b) To calculate the charge on each plate, we can use the formula Q = CV, where C is the capacitance and V is the voltage. In this case, the voltage is the same as the battery voltage, so we can use the value of the battery to calculate the charge. The formula becomes Q = C x E, where E is the electric field between the plates. So, for this problem, the charge on each plate would be the capacitance (in farads) multiplied by the electric field (in volts per meter).

c) To calculate the electric field halfway between the plates, we can use the formula E = V/d, where V is the voltage and d is the distance between the plates. In this case, the voltage is the same as the battery voltage, so we can use the value of the battery to calculate the electric field. The formula becomes E = V/d, where d is the distance between the plates (in meters). So, for this problem, the electric field halfway between the plates would be the battery voltage (in volts) divided by half of the distance between the plates (in meters).

d) To calculate the work done by the battery to charge the plates, we can use the formula W = QV, where W is the work, Q is the charge, and V is the voltage. In this case, the voltage is the same as the battery voltage, so we can use the value of the battery to calculate the work. The formula becomes W = Q x E, where E is the electric field between the plates. So, for this problem, the work done by the battery would be the charge (in coulombs) multiplied by the electric field (in volts per meter).

For the second problem, you are correct that it involves