18

Question 1

For current to flow

Answer 1

• Needs a complete circuit

- something to push it around the circuit (by cell, battery or power supply)

Question 2

Good conductors

Answer 2

Most metals: copper, silver, gold and water

Question 3

Bad conductors

Answer 3

Good insulators: polymers such as Perspex or poly theme, wood and glass

Question 4

What is a electric current

Answer 4

• a flow of electrical charge
• in a metal, current is a flow of electrons
• Si unit - ampere
• 1milliamp =10^-3
• 1microamp = 10^-6

Ammeter - measures electrical current

Question 5

Why are things good conductors

Answer 5

Because they contain electrons that can move about freely within material

• a voltage is provided by a battery or power supply
• a voltage can start these conducting electrons moving in one direction through a he metal

Question 6

Electrons

Answer 6

A negative electric charge -> attracted to the positive terminal of the battery

Question 7

Conventional current

Answer 7

Flows (a flow of positive flow) moving + to -

Question 8

Electron flow

Answer 8

Electron flow ( a movement of conducting electrons) from - to +

Question 9

Current: symbol, unit and symbols for unit

Answer 9

I - quantity symbol
Amps - unit
A - symbol for unit

Question 10

Charge: symbol, unit and symbols for unit

Answer 10

Q-symbol for quantity
Coulombs - unit
C - symbol for unit

Question 11

Time: symbol, unit and symbols for unit

Answer 11

t - symbol for quantity
Seconds - unit
s - symbol for unit

Question 12

Meaning of current

Answer 12

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

Question 13

Trip switches

Answer 13

Power supplies are protected by trip switches to cut out if to large current flow

Question 14

The current following

Answer 14

Controlled by the electrical resistance to the circuit
Measured in ohms

Resistance = p.s (v) / current (A)

R = V/I

Question 15

Changing current

Answer 15

The greater the resistance => the smaller the current

The greater the p.d => the greater the current that flows

Question 16

Through think and thin wire

Answer 16

Longer the wire, greater resistance

Smaller the diameter of wire => greater the R

Question 17

Potential difference

Answer 17

Is and the term for voltage as it is measured in volts(V) using a Voltmeter
Special name for p.d across a cell = e.m.f also measured in volts
E.m.f = electro motive force
Any component that pushes current around a circuit is said to have an e.m.f

Question 18

E.m.f

Answer 18

P.d at the terminals when there is no current flowing, it is a voltages produced by a power source.

Energy transferred per coulomb/unit charge

Question 19

Equation for power

Answer 19

P= IV
Unit W

P= E/T
Energy transformed/ time taken

Question 20

Resistance equation

Answer 20

R=V/I

Unit Ohums

Question 21

Energy equation

Answer 21

E= IVT
(T = must always be in seconds)
Unit J

Question 22

Charge, current and time equation

Answer 22

Charge = I/T
Current = C/T 

*triangle.