Ch18 Electrical Quantities

Question 1

Define Current:

Answer 1

The rate at which electric charge passes a point in a circuit

Question 2

Define cell:

Answer 2

Device that provides an electromotive force (e.m.f) in a circuit by means of a chemical reaction

Question 3

Define battery:

Answer 3

2/more electrical cells connected together in a series

Question 4

Define direct current (d.c):

Answer 4

Electric current that flows in the same direction all the time

Question 5

Define alternating current:

Answer 5

Electric current that (periodically) changes direction

Question 6

Define conductor:

Answer 6

Material that allows an electric current to flow through it

Question 7

Define insulator:

Answer 7

A material that makes it very difficult for electrical current to flow through it

Question 8

Define charge:

Answer 8

Carried around a circuit by the current, negative charge is carried by electrons

Question 9

Define galvanometer:

Answer 9

A meter for measuring tiny electric current

Question 10

Define ammeter:

Answer 10

Meter for measuring electric current

Question 11

Define ampere, amps (A):

Answer 11

The SI unit of electric current

Question 12

What is the equation for current:

Answer 12

Current = charge/time

I = Q/t

Question 13

Define voltage:

Answer 13

The energy transferred/work done per unit charge
(Can be imagined as the push of a battery/power supply in a circuit)

Question 14

Define potential difference (p.d.) :

Answer 14

The work done by (a unit) charge passing through an electrical component

Another name for the voltage between two points

Question 15

Define volts (V):

Answer 15

The SI unit of voltage (p.d. Or e.m.f.)
1V = 1J/C

Question 16

Define voltmeter:

Answer 16

A meter for measuring the p.d. (voltage) between two points

Question 17

Define electromotive force (e.m.f.):

Answer 17

Electrical work done by a source (cell, battery, etc) in moving (a unit) charge around a circuit

The voltage across the terminals of a source

Question 18

What is the equation for potential difference?

Answer 18

P.d. = work done by the charge/charge

V =W/Q

Question 19

What is the equation for electromotive force?

Answer 19

E.m.f. = work done on the charge/charge

E = W/Q

Question 20

Define resistance:

Answer 20

A measure of how difficult it is for an electric current to flow through a device/a component in a circuit

It is the p.d. across a component divided by the current through it

Question 21

What is the equation for resistance:

Answer 21

Resistance = p.d./current

R = V/I

Question 22

Define ohm (Ω):

Answer 22

The SI unit of electrical resistance
1Ω = 1V/A

Question 23

Define current voltage characteristics:

Answer 23

A graph of current on the vertical axis and voltage on the horizontal axis

Question 24

Define electrical power:

Answer 24

Power = current x p.d.

P = VI
(Watts = amps x volts)

Question 25

What is the equation for energy transferred?

Answer 25

Energy transferred = current x p.d. x time

E = IVt

Answer in joule

Energy transferred = power x time
(kWh) (kW) (Hours)

E = P x t

Question 26

Define electric current:

Answer 26

The rate of flow of charge

Question 27

Define terminal potential difference:

Answer 27

The potential difference that is measured across the terminals of a real battery in a closed circuit.

*it will be less than the battery’s rated emf because as charge passes through the electrolyte of the battery, it meets some resistance and loses energy

However if t.p.d. is measured when the circuit is open (no current), the battery’s terminal potential difference will equal the battery’s emf