Dads View

How do you measure voltage in a circuit?

Yes, you need to use a voltmeter or a multimeter with a voltage scale.

Voltage is always measured with respect to 2 points in an electrical circuit.

Most DC circuits use a common output of the power supply(usually the negative) for one of the points and call this ground (abbreviated GND). The black terminal of your meter should be attached to this point, while the red lead is used to measure voltages in the rest of the circuit with respect to this ground point.

If you have an Ultracapacitor with the below specs…

Boostcap® Ultracapacitor
3000.0 Farad ± 20%; 2.7V
How many would you need to store 1KWH of energy? ( 1,000 watts for an hour)

The energy in Joules stored in a capacitor can be calculated with the following formula

E=(1/2) C V^2

for C=3000F V=2.7 Volts

E=10935 Joules

1Kwh = 3,600,000 Joules

Therefore you would need

3600000/10935 = 329.2 or rounding up

330 capacitors to supply 1Kwh of energy

Modern ultracapacitors are now approaching the energy density of the best batteries and have the advantage of very rapid charge and discharge currents

The device shown at the following link is very similar to the calculated result shown above
Capacitor Bank

Two inductors having inductances L1= 5H and L2=2H and are connected in parallel. The mutual inductance M between the two inductors is 1H. Determine the equivalent inductance (in H) for this system.

With mutual inductance the combined inductance is more complicated to calculate

M=1H

1/Ltotal =( L1 + L2 - 2(M)) / (L1L2 - M^2)
1/Ltotal = (7-2) / (10-1)
1/Ltotal = 5/9

Ltotal = 1.8 H

See also this page for future reference
Series and parallel circuits

The primary purpose of diodes is to allow electrical current to flow in only one direction.

The primary purpose for power diodes is as components of power supplies that are used to convert AC (Alternating Current) line voltage (from the wall socket) into DC (Direct Current) to power an electronic device.

Diodes are typically rated based on 2 numbers:

(1)Maximum current they can carry
(2)The maximum reverse voltage they can withstand (also called PIV or Peak Inverse Voltage)