Capacitance - 23

Question 1

Define capacitance

Answer 1

Charge stored per unit of P.D

Question 2

Charge stored on a capacitor is directly proportional to what?

Answer 2

The potential difference across it.

Question 3

what does C represent

Answer 3

Capacitance

Question 4

What is capacitance measured in ?

Answer 4

Farads (F)

Question 5

When a capacitor is connected to a power supply what happens, in terms of the electrons?

Answer 5

Electrons move from the battery onto one of the plates which becomes negatively charged

Question 6

What happens to the positive plate when the battery is plugged into the capacitor?

Answer 6

electrons move from he positive plate to the battery

Question 7

What type of field is created between the two plates of a capacitor?

Answer 7

Electric field

Question 8

If the capacitor is disconnected from the battery across a resistor what happens?

Answer 8

It discharges

Question 9

What does A represent when referring to capacitance?

Answer 9

Area of overlap

Question 10

What is epsilon 0?

Answer 10

permittivity of free space - 8.85x10-12

Question 11

What does epsilon r reprisent?

Answer 11

relative permittivity of the dielectric places between the plates

Question 12

What is a dielectric?

Answer 12

An insulator places between the plates of a capacitor

Question 13

The charge of a capacitor increases with what?

Answer 13

potential difference - straight line from bottom left to top right

Question 14

What does E represent?

Answer 14

Energy stored in the capacitor (J)

Question 15

Energy stored is what on a Q/V graph?

Answer 15

area underneath

Question 16

what graph is the same when charging and discharging a capacitor?

Answer 16

Current (I) against time

Question 17

What two graphs flip when charging and discharging for a capacitor?

Answer 17

Charge and Voltage against time

Question 18

Current is initially high when?

Answer 18

start of charging a capacitor/ start of discharging

Question 19

What does the area under a Q/T graph represent?

Answer 19

Charge stored by the capacitor

Question 20

time constant is equal to what percentage fall in charge?

Answer 20

37%

Question 21

What are three uses of a capacitor?

Answer 21

smoothing unwanted voltage in a circuit, back up power supplies and timing circuits

Question 22

What is the charge on opposite capacitor plates?

Answer 22

equal and opposite

Question 23

What is used to charge a capacitor at a constant current/

Answer 23

a variable resistor

Question 24

How do you measure the potential difference of a capacitor?

Answer 24

using a high resistance voltmeter connected in parallel

Question 25

How do you test for how P.D changes with time for a capacitor?

Answer 25

use the variable resistor to keep the current constant and use a stopwatch and measure the voltmeter reading at constant intervals.

Question 26

What can be used to measure the energy transfer from a charged capacitor to a bulb?

Answer 26

a joulemeter