Electricity revision

Question 1

Define electric current

Answer 1

Rate of flow of charge

Question 2

What is the unit of charge

Answer 2

Coulomb

Question 3

What is e

Answer 3

elementary charge = 1.6 x 10^-19

Question 4

Why is net charge on a partice in terms of e

Answer 4

electrons are a fundemental particle

Question 5

How does current move in metals an electrolytes

Answer 5

In metals current flows as the movement of electrons
In electrolytes current flows as the movement of ions

Question 6

What is the difference between conventional current and electron flow

Answer 6

Conventional current = Flow from positive to negatiove terminal
Electron flow = Flow from negative to positive terminal

Question 7

Kirchoffs 1st Law

Answer 7

Conservation of charge. The sum of currents flowong into a junction is equal to the sum of currents flowing out of the juction

Question 8

What is mean drift velocity of charge carriers

Answer 8

Measure of the average distance they travel per unit time in the direction of the force

Question 9

What is the equation for I (n is the number density of charge carriers

Answer 9

I = Anev

Question 10

What is a conductor in terms of n

Answer 10

10^28 free electrons per cubic meter (high number density)

Question 11

What is a semiconductor in terms of n

Answer 11

10^17 free electrons per cubic meter

Question 12

What is an insulator in terms of n

Answer 12

Very low number density

Question 13

Define p.d

Answer 13

Measure of the transfer of energy by the charge carriers.

Question 14

what is emf and how can it be used to describe a source

Answer 14

Measure of the transfer of energy to the charge carriers (the greater the emf the more energy per coulomb has been transferred into electrical energy)

Question 15

What is emf measured in

Answer 15

Volts

Question 16

Define eV and its equation

Answer 16

Work done on a single electron travelling from the cathode to the anode
eV=0.5xmv^2

Question 17

What is ohms law

Answer 17

For a metallic conductor kept at a constant temperatutre I is proportional to V

Question 18

Voltage in vs voltage out equation

Answer 18

Vout = Vin (R2/RT)

Question 19

Emf equation

Answer 19

Terminal pd + Lost volts

Question 20

Resistivity equation

Answer 20

Resistance / (length x area)

Question 21

How is resisistivity affected by temp in a metal

Answer 21

As temp increases, resistivity in a metal increases (conductivity decreases)

Question 22

what is a kilowhatt hour

Answer 22

unit of energy. Kw x h

Question 23

kirchoffs 2nd law

Answer 23

around any closed loop in a circuit, the directed sum of potential differences across components is zero (conservation of energy)