Study 2 - 17th September

Question 1

What is the measuring unit of charge

Answer 1

Coulomb

Question 2

One coulomb is the total charge of how many electrons

Answer 2

6.25 x 10^18

Question 3

A single electron has a charge of what

Answer 3

1.6 x 10^-19C

Question 4

The total charge is given by what

Answer 4

Q = number of electrons
———————————C
6.25 x 10^18

Question 5

A charge of 1.6 x 10^-19 represents what

Answer 5

1e^-

Question 6

What is the charge of 5000 electrons

Answer 6

Q = number of electrons
—————————— C
6.25 x 10^18

    =

Q = 5,000
——————— C = 8 x 10^-16 C
6.25 x 10^18

“Tip— Write your rough work to get marks for it

Question 7

Use n as a representation for number of electrons

Answer 7

Q = ? ( unknown quantity )
n = 5,000

Q = n
———————-
6.25 x 10^18

= 5,000
———————-
6.25 x 10^-18

=

Question 8

Take for e.g a charge of 3 coulombs

Answer 8

Q = 3C
n = ?

Q = n
————
6.25x10^18

=. n = Q x 6.25 x 10^18 —- transposing formula

n = 3 x 6.25 x 10^18 = 18.75 x 10^18 e^-

Question 9

There is some similarity between a hydrualic system and an electric system

Answer 9

Charge is similar to water

Question 10

what is Voltage

Answer 10

Voltage is defined as energy ( W ) per unit of charge ( Q )

Question 11

Give the formula to find voltage, and explain what each symbol in the formula means

Answer 11

V = W
—-
Q

W is expressed in Joules, Q in coulombs and V in volts

Question 12

What is energy

Answer 12

The ability to do work

Question 13

In the voltage formula, what does Q represent

Answer 13

Charge

Question 14

In the voltage formula, what does W represent

Answer 14

Energy

Question 15

In the voltage formula, what does V represent

Answer 15

Voltage

Question 16

What is a voltage source

Answer 16

A voltage source is a source of electrical potential energy or electromotive force, more commonly known as voltage

Question 17

What do batteries convert

Answer 17

Batteries convert chemical energy into electrical energy

Question 18

What do generators convert

Answer 18

Generator converts mechanical energy into

Question 19

What is ionization

Answer 19

The neutral atom becomes a positive ion

Question 20

What is electricity? simple definition for yourself

Answer 20

Charges moving

Question 21

What is electrical current

Answer 21

Electrical current ( I ) is rate of flow of charge

Question 22

What is the formula for electrical current

Answer 22

I = Q
—-
t

Question 23

What unit is electrical current measured in

Answer 23

Ampere ( A )

Question 24

What unit is time measured in

Answer 24

Seconds ( s )

Question 25

What is 1C equal to

Answer 25

1A ( amp ) x 1s ( seconds)(time)

Question 26

• 3C of charge flow past a given point in a wire in 12s. What is the current in the wire?

If the current is 3, calculate the amount of charge passing by a given point in 5s?

Calculate the corresponding number of electrons

Answer 26

Q = 3C
t = 12s
I = ?

1. Q
   —-
   t

I = 3C
—— = 0.25A
12s

2. I = 3A - we will say A because question didnt tell us
   Q = ?
   t = 5s

I = Q <=> Q = I x t ( transposed suit the q)
——
t
Q = 3A x 5s = 15C

3. Q = 15C
   n = ?

Q =. n. <=>. n = Q x 6.25x10^18
———————
6.25 x 10^18

n = 15 x 6.25 x 10^18 = 9.375 x 10^19

Question 27

What is resistance

Answer 27

Resistance is the opposition to current

Question 28

What do electrons collide with while moving

Answer 28

Atoms

Question 29

When do electrons lose energy and release heat

Answer 29

When they collide with atoms

Question 30

different materials have different what?

Answer 30

Resistance

Question 31

What is the unit of resistance

Answer 31

ohm ( Ω )