Capacitors

Question 1

State an application of a capacitor

Answer 1

In an electronic timer

Question 2

what is the overall charge of a capacitor

Answer 2

One plate has a Q+ charge and the other parallel plate has a Q- charge so the overall charge is Q

Question 3

Define capacitance

Answer 3

The capacitance of a capacitor is the charge stored per unit of potential difference across it

or
Q
C= —
v

Question 4

What is the unit of capacitance

Answer 4

The Farad = CV-1

Question 5

What is the equation for the energy stored in a capacitor

Answer 5

W=0.5Cv2

Question 6

If W=0.5CV^2 by substituting Q=CV what two equations can you form

Answer 6

1) W=0.5CV^2

    Q^2 2)W=---------
      2C

Question 7

For capacitors in parallel what is the capacitance total

Answer 7

C total= C1 + C2

Question 8

For capacitors in Series what is the capacitance total

Answer 8

1 1 1
———- = ———— + ———–
C total C1 C2

Question 9

How do you calculate the total charge stored in a capacitor

Answer 9

Q= C total x V

Question 10

What type of graph represents the discharge of a capacitor

Answer 10

Exponential decay graph

Question 11

How does a capacitor discharge

Answer 11

When it is connected in a circuit parallel to a resistor causes a current to flow in the circuit so the electrons on the charged plate of the capacitor will be free to leave and flow in the circuit lowering the pd of the capacitor

Question 12

What is the general equation for the discharge of a capacitor

Answer 12

1
- ——-
CR
x=x0e

Question 13

Define the time constant

Answer 13

The time constant is the time taken for the current, charged stored or p.d to fall to e-1 about 37% of its initial value