Electricity

Question 1

What is a conductor? What is a good conductor and why?

Answer 1

Materials that allow the flow of electric charge. Metals are good conductors as the delocalized electrons are free to flow through the metal and so carry a current.

Question 2

What is a insulator? What is a good insulator and why?

Answer 2

Materials that do not allow the flow of electric charge. Plastic is a good insulator as it does not contain free electrons and so current is unable to flow.

Question 3

How do metals conduct electricity ?

Answer 3

The delocalized electrons involved in metallic bonding allow metals to conduct electricity

Question 4

What is an electric current and what are the 4 things needed for one to work?

Answer 4

A path for electric charge to flow along
-A source of energy
-A complete loop
-A component
-No short circuits

Question 5

Why do cables have plastic coatings?

Answer 5

Metals usually copper are used to make electrical wires because they conduct current, to prevent electrical shocks the metal wires are coated with a thick layer of plastic

Question 6

What is conventional current?

Answer 6

Positively charged particles moving from the positive terminal around a circuit to the negative terminal

Question 7

What is electron flow?

Answer 7

Charge carried by electrons, flowing from the negative terminal to the positive terminal

Question 8

In a series circuit if the circuit is broken anywhere, what will happen?

Answer 8

The current will not flow

Question 9

What are the nine circuit diagrams you need to know ?

Answer 9

Switch Cell. Battery
Resistor Variable Resistor Lamp
Voltmeter Ammeter. Fuse

Question 10

What is a series circuit?

Answer 10

One in which the components are arranged one after another

Question 11

What is cell polarity?

Answer 11

Is concerned with which end of a cell is positive and which end is negative, see figure 9.2 and 9.3

Question 12

What is the equation for charge? (Symbol, word and measured in)

Answer 12

Q = I x t
Charge = current x time
Charge - Coulombs (C)
Current - Amperes (A)
Time - Seconds (s)

Question 13

What is ohms law?

Answer 13

That the current in a metallic conductor is directly proportional to the voltage across its ends provided the temperature remains constant

Question 14

How do you ensure the wire’s temperature remains constant in an experiment

Answer 14

-keeping the voltage low (current remains small)
-switching off the current between readings to allow the wire to cool

Question 15

Summary for an VI Graph

Answer 15

V ^ m=R
| / High resistance = large m
| / Low resistance = small m
| /
| /
|/_____________>
I

Question 16

Summary of an IV graph

Answer 16

V ^ m=I/R
| / High resistance = small m
| / Low resistance = large m
| /
| /
|/_____________>
I

Question 17

What is an ohmic conductor

Answer 17

-Is one in which the potential difference is directly proportional to the current passing through it
-provided the material is maintained at a constant temperature

Question 18

What is the equation for voltage? (Symbol, word and measured in)

Answer 18

V = I x R
Voltage = current x resistance
Voltage - volts/V
Current- Amps/A
Resistance - Ohms/(~)

Question 19

Practical for a filament bulb

Question 20

Current in a series circuit is? Voltage in a series circuit is?

Answer 20

The current flowing through a series circuit is the same everywhere
Voltage of the supply is equal to the sum of the voltages across the separate components in a series circuit. (Ein = Eout hence supply voltage = V1 + V2 + V3 etc)

Question 21

Voltage in a parallel circuit is? Current in a parallel circuit is ?

Answer 21

The voltage across each component in a parallel circuit is the same as
that of the supply( 1/Rt = 1/R1 + 1/R2 + 1/R3 etc )
The total current taken from the supply is the sum of the currents through the separate components in a parallel circuit.

Question 22

Resistance and length Graph. What are the results?

Answer 22

The graph is a straight line that passes through the origin; and
- this shows that for a metal wire at constant temperature the resistance and length of wire are proportional

Question 23

Graph of resistance against CSA equation? (Symbol, word and measured in)

Answer 23

R = k x L
Resistance = Resistance x Length
Resistance = Ohms/ (~)
Resistance = ohms/meter (~)/m
Length- Metres/m

Question 24

The resistance of a piece of wire depends on several factors. What are these factors?(summary)

Question 25

How does Resistance change with L? 3 graphs

Answer 25

R^.
|. /
|. /
|. /
| /
|/____________>L.

R^
|.
|—————
|.
|
|____________>L

R^
||
|. \
|. \
| \_____
|_____________>L

Question 26

When electrical current flows through a metal wire it generates heat. How?

Answer 26

When the electrons flow through a cable they can collide with atoms. The electrons lose kinetic energy which is passed on to the atoms. The atoms then vibrate more and the material heats up

Question 27

Equation for energy?

Answer 27

E = P x t
Energy = power x time
Energy - joules/ J
Power - watts/W
Time - seconds/s

Question 28

Equation for power?

Answer 28

P = I x V
Power = current x voltage
Power - watts/w
Current - amperes/A