Electrons Waves and Photons

Question 1

Definition of coulomb

Answer 1

One coulomb is the amount of charge which flows past a point in a circuit when a current of 1 ampere flows for 1 second

Question 2

Kirchoff’s First Law

Answer 2

In a network of steady currents, the algebraic sum of the currents at any junctions is equal to zero (I1 + I2 = I3)

Question 3

Electron drift velocity equation

Answer 3

I = Anev
I = current
A = cross sectional area
n = number density of charge carriers
e = electron charge

Question 4

Define potential difference

Answer 4

The potential difference between two points in a circuit is equal to the amount of electrical energy converted to other forms per coulomb of charge flowing between them

Question 5

Define volt

Answer 5

The volt is equal to the p.d. Between two points in a circuit, when 1 joule of electrical energy is converted to other forms when 1 coulomb of charge passes between them

Question 6

Energy transferred equation

Answer 6

W = VIt

Question 7

Define electronvolt

Answer 7

One electronvolt is the energy transferred when an electron travels through a potential difference of one volt.

Question 8

Define electromotive force

Answer 8

The e.m.f of a cell or other devices is the energy converted to electrical form from other other forms for each unit of charge passed through a device

Question 9

Define resistance

Answer 9

The resistance of the component is defined as the ratio of the potential difference V, across it to the current I, flowing through it

Question 10

Define ohm

Answer 10

The ohm is the resistance in which a current of 1A produces a pd of 1V

Question 11

Ohm’s Law

Answer 11

The current through a metallic conductor is directly proportional to the pd across its ends, providing that its temperature and other physical conditions remain constant

Question 12

Resistivity equation

Answer 12

R = pL/A

Question 13

Define resistivity

Answer 13

Resistivity can be defined as numerically equal to the resistance of a sample of the material of unit length and unit cross sectional area at a particular temperature

Question 14

Effect of temperature on a metals resistance

Answer 14

Temperature increases the resistance of a metal

Question 15

What happens to resistance of insulators as temperature increases

Answer 15

The resistance of insulators does not ch she as temperature increases

Question 16

What effect does temperature have on semiconductors

Answer 16

The resistance decreases exponentially with temperature

Question 17

Cost of energy

Answer 17

Cost = kWh x p

Question 18

Define Kirchoff’s second law

Answer 18

In any closed loop in any circuit of steady currents, the sum of emf’s acting is equal to the sum of the pd’s

Sum emfs = sum IR

Question 19

Internal resistance equations

Answer 19

Emf = IR(terminal pd) + Ir(lost volts)

Emf = V + Ir

Question 20

Define internal resistance

Answer 20

The ratio of the lost volts to the current flowing through the source is called the internal resistance