Electricity

Question 1

What is Conventional Current Flow?

Answer 1

Flow from positive to negative in a circuit

Question 2

How is current measured?

Answer 2

In Amperes, symbol I

Question 3

What is the function of a Diode?

Answer 3

Allows current to flow in one direction only

Question 4

What is the typical threshold voltage for diodes?

Answer 4

Approximately 0.7 V

Question 5

Define Electromotive Force (EMF)

Answer 5

The energy per unit charge transferred electrically by a source, measured in V.

Question 6

What is Electron Flow?

Answer 6

Flow of electrons from negative to positive in a circuit

Question 7

What is Internal Resistance?

Answer 7

Resistance within a power source that dissipates energy

Question 8

State Kirchoff’s First Law

Answer 8

Total current entering a junction equals total current leaving a junction

Question 9

State Kirchoff’s Second Law

Answer 9

Sum of EMF in any loop equals sum of potential differences of each component

Question 10

What are Light Dependent Resistors (LDR)?

Answer 10

Resistance decreases as light intensity increases

Question 11

What defines an Ohmic Conductor?

Answer 11

Follows Ohm’s law, where current is directly proportional to potential difference at constant temperature.

Question 12

What is Ohm’s Law?

Answer 12

Electric current is proportional to potential difference at constant temperature

Question 13

What is a Parallel Connection?

Answer 13

Components on separate loops with the same potential difference

Question 14

Define Potential Difference

Answer 14

The transfer of electrical energy per unit charge to other form of energy between two points in a circuit.

Question 15

What is a Potential Divider?

Answer 15

Combination of resistors in series that splits potential difference

Question 16

How is Power calculated in a circuit?

Answer 16

Product of current and potential difference, measured in Watts

Question 17

What is Resistance?

Answer 17

Measure of the opposition to flow of current, measured in Ohms, symbol R and is found by the ratio of V/I.

Question 18

Define Resistivity

Answer 18

Difficulty for charge to travel through a material, measured in Ohm metres, symbol ⍴

Question 19

What are Semiconductors?

Answer 19

Materials that change resistance based on external conditions such at temperature and light levels.

Question 20

What is a Series Connection?

Answer 20

Components on the same loop with potential difference shared between them

Question 21

What is Terminal Potential Difference?

Answer 21

Actual potential difference across power source terminals, EMF minus lost volts

Question 22

What is a Thermistor?

Answer 22

Resistance decreases as temperature increases

Question 23

What are Variable Resistors?

Answer 23

Resistors with adjustable resistance, used to change circuit voltage

Question 24

What is the purpose of a Voltmeter?

Answer 24

Measures potential difference between two points, ideally has infinite resistance

Question 25

Define current

Answer 25

Rate of flow of charge

Question 26

Define a charge carrier, n

Answer 26

An electron detached form its atom or an ion in a conducting material that is free to flow in order to create a current

Question 27

What is the difference between thermal energy and heating in terms of a hot filament?

Answer 27

The hot filament is hot and has a thermal energy (store), it transfers energy to its surrounding (HOT to COLD) via heating.

Question 28

What is a volt?

Answer 28

Where 1 joule of energy is transferred when 1 C of charge passes between two points in a circuit.

Question 29

Define 1 ohm

Answer 29

when a potential difference of 1 V across a component produces a current of 1A through it.

Question 30

How do you calculate the power dissipated in a wire?

Answer 30

It is best to use

Question 31

Define positive temperature coefficient

Answer 31

when a materials resistivity increases when temperature increases. (like a wire)

Question 32

Define negative temperature coefficient

Answer 32

when a materials resistivity decreases when temperature increases. (like a thermistor)

Question 33

As a rule of thumb....The total resistance of resistors in parallel...

Answer 33

Is always smaller than the smallest resistor.

Question 34

What is the difference between a rheostat and a potentiometer.

Answer 34

A rheostat in series control current, a potentiometer in parallel controls voltage.

Question 35

What is the breakdown voltage of a diode.

Answer 35

the minimum reverse voltage at which a significant current begins to flow through the diode in the opposite direction

Question 36

How can the EMF of a cell be measured?

Answer 36

Connect a very high resistance voltmeter (multimeter voltmeter) across it so that no current is drawn from the battery - no lost volts