current, potential difference and resistance

Question 1

What is electric current ?

Answer 1

It is a flow of electrical charge

Question 2

What is current measured in ?

Answer 2

Amperes

Question 3

What is charge measured in ?

Answer 3

Coulombs

Question 4

What is potential difference ?

Answer 4

The difference in the amount of energy that charge carriers between two points in a circuit

Question 5

What is the unit for potential difference ?

Answer 5

Measured in volts

Question 6

What is resistance ?

Answer 6

Resistance is a measure of the opposition to current flow in an electrical circuit.

Question 7

What is the unit for resistance ?

Answer 7

Measured in ohm

Question 8

What is the relationship between current, potential difference and resistance?

Answer 8

The current flowing through is directly proportional to to the potential difference across it

Question 9

What is the equation for potential difference ?

Answer 9

Potential difference (volts) = current (amps) x by resistance (Ω - ohms)

                                                       V   =  I  X   R

Question 10

Explain an Ohmic conductor ?

Answer 10

Current is directly proportional to potential difference

You get a straight line

Question 11

Explain a filament lamp ?

Answer 11

Temperature increases as current increases

Resistance increases

Harder for current to flow

Graph gets less steep

Question 12

Explain a diode ?

Answer 12

Current only flows in 1 direction

Has a high resistance in the reverse direction

Question 13

What does LDR stand for ?

Answer 13

Light dependent resistor

Question 14

Facts about LDR

Answer 14

Resistance of LDR changes as intensity of light changes

Bright light = low resistance

Darkness = high resistance

Question 15

Advantages of LDR

Answer 15

Automatic night lights

burglar detectors

Question 16

What is a thermistor ?

Answer 16

A temperature dependent resistor

In hot conditions the resistance drops

In cool conditions the resistance goes up

Used in car engines

Thermostats turn heating on when its cool and off when its warm

Question 17

What is the difference between series and parallel circuit ?`

Answer 17

If there are no branches then it’s a series circuit. If there are branches it’s a parallel circuit.

Question 18

How do you get from

kilogram to gram

centimetres to metres

Kilowatt to watt

Amps to milliamps

Answer 18

kg - g = x 1000
cm - m = ÷ 100
kilowatt - watt = x 1000
amps-milliamps = x1000

Question 19

Physics units

Answer 19

Quantity Unit Symbol
—————————————————————————-
Mass Kilogram kg
Length metre m
Time seconds s
Force Newton N
Energy Joules J
Temperature degree Celsius °C
Area square metre m2
Volume cubic metre m3
Power watt W
Frequency hertz Hz
Potential Difference volt V
Current ampere A
Resistance ohms Ω
Charge coulombs C