Chapter 12,13

Question 1

What is charged carriers

Answer 1

Charged particles that move through a substance when pd is applied across it.

Question 2

Insulators

Answer 2

In an insulator each electron is attached to an atom and cannot move away from the atom. When a voltage is applied across an insulator no current passes through the insulator because no electrons can move through the insulator

Question 3

Metallic conductor

Answer 3

More electrons are attached to atoms but some are delocalised
When voltage is applied across the metal these conduction electron are attracted towards the positive terminal o father metal.

Question 4

Semiconductor

Answer 4

The number of charge carries increases with an increase of temperature
The resistance of a semiconductor therefore decreases as its temperature is raised

Question 5

Potential difference

Answer 5

Work done or energy transfer per unit charge between two points when charge moves from one point to the other.

Question 6

Battery and of pd

Answer 6

A battery has the potential to transfer energy from its chemical store if the battery is not part of a complete circuit.
Each electron passing through a circuit component does work to pass through the component and therefore transfers some or all of its energy.
The work done by an electron is equal to its loss of energy the work done per unit charge is defined as pd

Question 7

EMF

Answer 7

The emf of a source of electricity is defined as the electrical energy produced per unit charge passing through the source. If electrical energy E is given to a charge Q in the source.

Question 8

Resistance

Answer 8

Resistance of a component in a circuit is a measure of the difficulty of making current pass through the component. Resistance is caused by the repeated collisions between the charge carries in the material with each other and with the fixed positive ions of the material.

Question 9

Ohms law

Answer 9

States that if the PD across a metallic conductor is proportional to the current through it, provided the physical conditions do not change.

Question 10

Resistivity

Answer 10

Resistivity is proportional of a material that defines the resistance for the resistor depending on its physical dimensions.

Question 11

Ammeter

Answer 11

Used to measure the current through the resistor. The ammeter must be in series with the resistor so the same current pass through both the resistor and the ammeter.

Question 12

Voltmeter

Answer 12

Used to measure the pd across the resistor, the voltmeter must be in parallel with the restart so that they have the same pd, no current should pass through the voltmeter.

Question 13

Variable resistor

Answer 13

Used to adjust the current and pd as necessary.

Question 14

Superconductivity

Answer 14

Superconductivity is a wire or device made of material that has zero Resistivity at and it decreases in temperature and when it hits below a critical temperature that depends on the material it then becomes superconductive.

Question 15

Circuits with Variable resistor

Answer 15

By using a variable resistor or a potential divider we can investigate how current and potential difference behave through a component and plot a I V graph
Current = i
PD = V

Question 16

Filament lamp

Answer 16

Filament lamp the current increases less rapidly as PD increases, this is because as current increases temperature increases which in turn causes in increase in resistance.

Question 17

A Diode

Answer 17

A dodge only allows current to flow in one direction. For all negative values of v1
i = O x A

Question 18

Positive temperature coefficient

Answer 18

The resistance of a metal increases when it’s temperature is increased

Question 19

Negative temperature coefficient

Answer 19

The resistance of a semiconductor decreases when its temperature is increased.

Question 20

Current and PD FOR a wire

Answer 20

Straight line going through 0

Question 21

Current and PD FOR a lamp

Answer 21

S line bottom half of s in -x and -y going through 0 and s top half of s on the y and x axis

Question 22

Current and PD FOR a thermistor

Answer 22

Two lines one for low and high temperature both going through 0

Question 23

Current Rules 1

Answer 23

At any junction in a circuit the total leaving the junction is equal to the total current entering the junction.

Question 24

Current rules 2

Answer 24

The current entering a component is the same as the current leaving a component.

Question 25

Current rule 3

Answer 25

The current passing through a two or more component in series is the same through each component

Question 26

Potential difference rules

Answer 26

If the charge carries lose energy the potential difference is a potential drop.

If the charge carries gain energy which happens when thy pass through a battery or cell the potential difference is a potential rise equal to the pd across the battery or cell terminal

Question 27

Resistors in series

Answer 27

In series pass the same current. The total PD is equal to the sum of the individual pds.

Question 28

Resistors in parallel

Answer 28

In parallel have the same pd. The current through a parallel combination of resistors is equal to the sum of the individual currents.

Question 29

Internal resistance

Answer 29

Of a source of electricity is due to opposition to the flow of charge through the source. This causes electrical energy produced by the source to be dissipated inside the source the when charge flows through it.

Question 30

Electromotive force

Answer 30

(EMF) of the source is the electrical energy per unit charge produced by the source. If electrical energy E given to a charge Q in the source,

ε= E/Q

Question 31

Pd across the terminals

Answer 31

The source is the electrical energy per unit charge delivered by the source when its is in a circuit. The terminal pd is less than the emf whenever current passes through the source. The difference is due to the internal resistance of the source.

Question 32

Internal resistance of a source

Answer 32

The loss of potential difference per unit current in the source when current passes through the source

Question 33

Potential divider

Answer 33

A potential divider consist of two or more resistors connected in series with a source of fixed PD

Question 34

PD is divided

Answer 34

Between the resistors proportional to their resistance

Question 35

Potential divider circuits

Answer 35

Can be used as sensors, by using a thermistor and a voltmeter, a thermostat can be set be set up to turn heating on/off if p.d. gets too low / high

Question 36

Circuit which has a divider

Answer 36

Change the brightness of the bulb, the brightness is controlled by using a variable potential divider, by changing the resistor, the resistance will change which will change the brightness of the bulb. If the resistor is high the bulb is dim, the opposite happens when the resistance is low.

Question 37

Sensor circuit

Answer 37

Produces an output p.d. which changes as a result of a change of a physical varaible such as temperature or light intensity.