P4- Electric circuits

Question 1

How do insulators become charged?

Answer 1

By rubbing another insulator on it, electrons are transferred from one material to the other

Question 2

When a cloth was rubbed against a rod the cloth became positively charged, why?

Answer 2

Negatively charged electrons were transferred from the cloth to the rod. More positive charges on the cloth

Question 3

What is an electric field and when is it strongest?

Answer 3

The surroundings of a charged object which creates a force. Strongest when distance between charged objects is small

Question 4

How does a non contact force occur?

Answer 4

When two charged objects exert a force on each other

Question 5

What happens to…
Same charges?
Dif charges?

Answer 5

Same charges repel
Dif charges attract

Question 6

Switch
What does it do?
How does it look?

Answer 6

Enables current to be turned on and off
Two circles with diagonal line between

Question 7

Cell
What does it do?
How does it look?

Answer 7

Pushed electrons around a circuit
Big line parallel to smaller line

Question 8

Battery
What does it do?
How does it look?

Answer 8

More than one cell
A cell with dashed line between

Question 9

Diode
What does it do?
How does it look?

Answer 9

Allows current to pass in the forward direction
Arrow in a circle

Question 10

Fixed resistor
What does it do?
How does it look?

Answer 10

Reduced the current
Rectangle

Question 11

Variable resistor
What does it do?
How does it look?

Answer 11

Allows current and resistance to be changed
Rectangle with arrow through it

Question 12

Light emitting diode (LED)
What does it do?
How does it look?

Answer 12

Emits light when current passes through it in a certain direction
Diode with arrows off it

Question 13

Lamp/bulb
What does it do?
How does it look?

Answer 13

Emits light when current passes through it
Circle with cross in it

Question 14

Fuse
What does it do?
How does it look?

Answer 14

Melts and breaks circuit is current is too high
Rectangle with line through it

Question 15

Voltmeter
What does it do?
How does it look?

Answer 15

Measure potential difference
Circle with V

Question 16

Ammeter
What does it do?
How does it look?

Answer 16

Measures current
Circle with A

Question 17

Thermistor
What does it do?
How does it look?

Answer 17

Resistance changes with temperature
Rectangle with hockey stick

Question 18

Light dependent resistor (LDR)
What does it do?
How does it look?

Answer 18

Resistance changes on amount of light
Rectangle in circle with arrows pointing to it

Question 19

Current?
Unit?

Answer 19

The flow of charge around a circuit
amps (A)

Question 20

Ammeter & voltmeter measures?
placed in?

Answer 20

Ammeter- Current, series
Voltmeter- Potential difference, parallel

Question 21

Resistance

Answer 21

Measure of how difficult it is for current to pass through a component

Question 22

Ohms law

Answer 22

The potential difference is directly proportional to the current when the temp is constant

Question 23

How to investigate the resistance of a wire based on length?

Answer 23

-Set up wire, ammeter & voltmeter in a circuit
-Attach a crocodile clip to start of wire and first specified length
-Record length, current & pd
-Switch of circuit, calculate resistance
-Vary length of wire, repeat

Question 24

What does a directly proportional graph look like?

Answer 24

Straight line through the origin

Question 25

How to investigate component characteristics

Answer 25

-Set up ammeter, variable resistor, component & voltmeter
-Record current and pd
-Switch off power supply
-Adjust resistance & take new reading
-After 5 readings, reverse terminals to take negative values
-Take another 5 readings, plot graph
-Repeat with other components

Question 26

Current-pd graph for a filament lamp
Ohmic conductor?
Increased pd..?
Increased temp..?

Answer 26

-Not an ohmic conductor
-As the pd increases, current and resistance increases
-If the temp increases, current and resistance increases

Question 27

Current-pd graph for a diode
Ohmic conductor?
Increased current..?
In reverse direction..?

Answer 27

-Not an ohmic conductor
-Current only flows in one direction
-In forward direction, as current increases, resistance increases
-In reverse direction, resistance is very high

Question 28

Current-pd graph for thermistors and LDRs
Ohmic conductors?
Temp/light increases..?

Answer 28

-Not ohmic conductors
-As temp or light intensity increase, resistance decreases

Question 29

In series circuit
Current is…?
Pd is…?
Resistance is…?

Answer 29

Same across each component
Shared between components
Added up across all, to give total resistance

Question 30

In series circuit, how to calculate..
Total current?
Total pd?
Total resis?

Answer 30

Same as single component
Add up pds of all components
Add up resis of all components

Question 31

In parallel circuit
Current is…?
Pd is…?
Resistance…?

Answer 31

Shared between branches
Same across all
Total res is less than the resistor with least resistance

Question 32

In parallel circuit, how to calculate..
Total current?
Total pd?
Total resis?

Answer 32

Add up current of all components
Same as single component
Less than the resistor with least resistance

Question 33

Series circuit
Components arranged in…
Routes?

Answer 33

Components arranged in a single chain
Current only has one route to take

Question 34

Parallel circuit
Components arranged in…
Routes?

Answer 34

Components arranged in branches
Current has more than one route to take