module 4 part 1 electricity

Question 1

Ohms law

Answer 1

The current and potential difference through an ohmic conductor
held under constant physical conditions are directly proportional, with the constant
of proportionality being resistance

Question 2

current

Answer 2

The rate of flow of charge in a circuit

Question 3

charge

Answer 3

a physical quantity, which can be either positive or negative. It is measured in coulombs (C)

Question 4

ions

Answer 4

an atom that has either lost or gained electrons and so has net charge

Question 5

conventional current

Answer 5

model used to describe electrical current in a circuit - conventional current travels from pos to neg - it is the direction in which pos charge would travel

Question 6

kirchoff first law and equation

Answer 6

at any point in an electrical circuit, sum of currents in that point is equal to sum of currents out, electrical charge conserved

∑I in=∑I out

Question 7

number density

Answer 7

the number of free electrons per cubic metre of a material, symbol n

Question 8

potential difference

Answer 8

energy transferred from electrical to other forms of energy (e.g. light) per unit charge. Work is done on component

Question 9

EMF

Answer 9

the work done on charge carrier per unit charge, measured across power supply.

Question 10

cathode and anode

Answer 10

anode - positively charged electrode

cathode - negatively charged electrode

electron flow moves from cathode to anode, conventional is opposite

Question 11

thermionic emission

Answer 11

the emission of electrons from surface of hot metal wire

Question 12

temp and res graph explained

Question 13

diode symbol and direction

Question 14

difference between emf and pd

Answer 14

Pd - energy transferred from electrical to other forms of energy (e.g. light) per unit charge. Work is done on component.

Emf - energy transferred from source of power (e.g. chemical energy) to charge carriers. Work done on charge carrier.

Question 15

Conservation of Charge

Answer 15

The total charge in a system cannot change

Question 16

Electrolytes

Answer 16

Substances that contain ions that when dissolved in a solution, act
as charge carriers and allow current to flow.

Question 17

Elementary Charge

Answer 17

The smallest possible charge, equal to the charge of an
electron

Question 18

Insulators

Answer 18

A material that has no free charge carriers and so doesn’t allow the
flow of electrical charge.

Question 19

Mean Drift Velocity

Answer 19

The average velocity of an electron passing through an
object. It is proportional to the current, and inversely proportional to the number of
charge carriers and the cross-sectional area of the object

Question 20

Quantisation of Charge

Answer 20

The idea that charge can only exist in discrete packets
of multiples of the elementary charge.

Question 21

Semiconductors

Answer 21

A material that has the ability to change its number of charge
carriers, and so its ability to conduct electricity. Light dependent resistors and
thermistors are both examples.

Question 22

Diode

Answer 22

A component that allows current through in one direction only. In the
correct direction, diodes have a threshold voltage (typically 0.6 V) above which
current can flow

Question 23

Electromotive Force

Answer 23

The energy supplied by a source per unit charge passing
through the source, measured in volts.

Question 24

Filament Lamp

Answer 24

A bulb consisting of a metal filament, that heats up and glows to
produce light. As the filament increases in temperature, its resistance increases
since the metal ions vibrate more and make it harder for the charge carriers to
pass through.

Question 25

I-V Characteristics

Answer 25

Plots of current against voltage, that show how different
components behave

Question 26

Kilowatt-Hour

Answer 26

A unit of electrical energy. It is usually used to measure domestic
power consumption.

Question 27

Light-Dependent Resistor

Answer 27

A light sensitive semiconductor whose resistance
increases when light intensity decreases

Question 28

Ohmic Conductor

Answer 28

A conductor for which the current flow is directly proportional
to the potential difference across it, when under constant physical conditions

Question 29

Ohm’s Law

Answer 29

The current and potential difference through an ohmic conductor
held under constant physical conditions are directly proportional, with the constant
of proportionality being resistance.

Question 30

Potential Difference

Answer 30

The difference in electrical potential between two points in a
circuit. It is also the work done per coulomb to move a charge from the lower
potential point to the higher potential point. It is measured in Volts

Question 31

Power

Answer 31

The rate of energy transfer in a circuit. It can be calculated as the product
of the current and the potential difference between two points. It is measured in
Watts

Question 32

Resistance

Answer 32

A measure of how difficult it is for current to flow through a material

Question 33

resistivity

Answer 33

A measure of how difficult it is for charge to travel through a material.
It is proportional to the object’s resistance and cross-sectional area, and inversely
proportional to the object’s length. It is measured in Ohm metres