Electricity

Question 1

What is charge?

Answer 1

Forcefield around a charged particle

Question 2

What is charge measured in?

Answer 2

Coulombs

Question 3

Define current

Answer 3

Charge per unit time

Question 4

What is one amp equivalent to?

Answer 4

One Coulomb per second

Question 5

Define voltage

Answer 5

Energy per unit charge

Question 6

What is one volt equivalent to?

Answer 6

One Joule per Coulomb

Question 7

Define energy/work in the context of electricity

Answer 7

Energy/work is the useful commodity moved around by electrons and is measured in Joules

Question 8

What is power?

Answer 8

Energy per unit time

Question 9

What is resistance?

Answer 9

Opposition to electric current

Question 10

What is the unit for resistance?

Answer 10

Ohms (Ω)

Question 11

State Ohm’s Law

Answer 11

Voltage is directly proportional to current, at constant temperature

Question 12

What does the gradient of an I/V graph represent?

Answer 12

1/R

Question 13

What is a superconductor?

Answer 13

Material with zero resistivity

Question 14

What is critical temperature?

Answer 14

Temperature below which a material becomes a superconductor

Question 15

What makes a material a good conductor?

Answer 15

A good conductor has free charge carriers that can move easily when a potential difference is applied.

Question 16

What is static electricity?

Answer 16

Static electricity is the build-up of charge on the surface of an insulator

Question 17

How should ammeters be placed in a circuit?

Answer 17

In series

Question 18

How should voltmeters be placed in a circuit?

Answer 18

In parallel

Question 19

What is the resistance of an ideal ammeter?

Answer 19

Zero

Question 20

What is the resistance of an ideal voltmeter?

Answer 20

Infinite

Question 21

In a series circuit, how is current and voltage distributed?

Answer 21

Current is the same everywhere, voltage is shared

Question 22

In a parallel circuit, how is current and voltage distributed?

Answer 22

All branches have the same voltage, current is shared

Question 23

More components are added in series?

Answer 23

Total resistance increases.

Question 24

More components are added in parallel?

Answer 24

Overall resistance decreases

Question 25

Kirchhoff's First Law

Answer 25

Total current going into a junction is equal to the total current coming out

Question 26

How is current divided at a junction?

Answer 26

Current is shared based on the resistance of each branch

Question 27

What does Kirchhoff's Second Law state?

Answer 27

The sum of all the voltages in a closed loop is equal to zero

Question 28

Kirchhoff's Second Law a version of which princple?

Answer 28

Conservation of energy

Question 29

What is a potential divider?

Answer 29

Two resistors connected in series to achieve a lower output voltage

Question 30

What is a potentiometer?

Answer 30

A variable resistor with three contacts, used as a variable potential divider

Question 31

What is an NTC thermistor?

Answer 31

Negative temperature coefficient (NTC), as temperature goes up resistance goes down

Question 32

What is the function of a diode?

Answer 32

Acts as a one-way valve, allowing current to flow in one direction only.

Question 33

What is the threshold voltage in a diode?

Answer 33

The minimum voltage required for current to flow through the diode.

Question 34

What direction is conventional current?

Answer 34

Positive to negative

Question 35

What is internal resistance?

Answer 35

Resistance of a cell ## Footnote Cells are not superconductors; thus, they have internal resistance that consumes some voltage before current leaves the cell.

Question 36

What is electromotive force (EMF)?

Answer 36

The total amount of energy the power supply gives to each coulomb ## Footnote EMF is different from terminal potential when the circuit is in use due to internal resistance.

Question 37

Another way of thinking about EMF?

Answer 37

It's the terminal potential of a cell when there's no current is flowing through it ## Footnote This means that the EMF reflects the maximum potential difference of the cell.

Question 38

What happens to terminal potential as current in the circuit increases?

Answer 38

The terminal potential always decreases ## Footnote This is due to the increase in 'lost volts' as current increases.

Question 39

How can you easily find the EMF of a cell?

Answer 39

By connecting a voltmeter across the ends of the cell ## Footnote This provides a direct measurement of the EMF.