Electrcity 1

Question 1

Like charges …….. while unlike charges…….

Answer 1

Repel

Attract

Question 2

What happens when you rub a polythene rod with a duster?

Answer 2

Electrons move from the duster to the polythene rod making the polythene negative and the duster positive

Question 3

What happens when you rub a acetate rod with a duster?

Answer 3

Electrons move from the rod to the duster making the acetate positive and the duster negative

Question 4

Define electric current?

Answer 4

The rate of flow of charge

Question 5

Current, charge and time in an equation ?

Answer 5

I = Q/t

Question 6

How many amps in 1 mA?

Answer 6

10*-3A

Question 7

What’s the charge of an electron?

Answer 7

1.6 x 10*-19 C

Question 8

What are the properties of a series circuit?

Answer 8

• current remains the same
• resistance is split
• voltage is split (Kirchhoffs law)

Question 9

What are the properties of a parallel circuit?

Answer 9

• the current splits down each branch
• resistance 1/RT = 1/R1 + 1/R2
• potential difference stays the same

Question 10

What’s a charge carrier?

Answer 10

It’s either an electron detached from its atom or an ion in a conducting material that’s free to flow in order to create a current

Question 11

Electrons in a metal move with …….. ……….. ………..

Answer 11

Random thermal motion

Question 12

What direction does the current flow?

Answer 12

From positive to negative

big line to small line in a cell

Question 13

What do the layers stand for in I = nAvq

Answer 13

I = current 
A = area of cross-section of conductor 
n = number if charge carriers per cubic meter 
v = drift velocity of charge carrier

Question 14

A real insulator has a very small ……

Answer 14

Number if charge carriers per cubic meter

Question 15

Define potential difference?

Answer 15

Between 2 points in a circuit is the electrical energy per unit charge converted into other forms of energy

Question 16

What does the cell do?

Answer 16

• it produces an electromotive force which creates pd in a circuit
• the charges feel a force si they move, creating a current

Question 17

What does the pd do?

Answer 17

It does work on the charges creating power

Question 18

Voltage, work done and charge?

Answer 18

Volatage = W / Q

Question 19

To reduce the a,punt of current in the voltmeter it must have a very high ……….

Answer 19

Resistance

Question 20

Define electromotive force?

Answer 20

Is the energy per unit charge converted into electrical energy by the source

Question 21

Electromotive force is actually an …………

Answer 21

Energy transfer

Question 22

Work done, charge and electromotive force?

Answer 22

E = W/Q

Electromotive force is measured in V

Question 23

Emf is the …….. and pd is the ………

Answer 23

Cause

Effect

Question 24

What’s emf?

What’s pd?

Answer 24

• emf: is the creation of electrical energy from other forms of energy
• pd: is the conversion of electrical energy into other forms of energy

Question 25

What’s the power rating?

Answer 25

The highest amount of power that can flow through a device

Question 26

Filament lamps are ........

Answer 26

Inefficient

Question 27

What’s a rheostat?

Answer 27

- it’s a variable resistor - when it’s used to continuously produce a variable potential difference it’s called a potential divider ( aka potentiometers)

Question 28

What’s ohms law?

Answer 28

It states that for metals at a constant temperature, the current in the metal is proportional to the pd across it

Question 29

Define resistance

Answer 29

Opposition to an electrical current flowing through it

Question 30

What causes resistance?

Answer 30

- it’s caused by collisions of the electrons with the vibrating lattice ions, as the electrons move through the conductor - these collisions cause energy to dissipate as thermal energy