Electricity

Question 1

Equation for current : current, charge and time

Answer 1

I= Q/t

Question 2

Equation for voltage: voltage, electrical energy and charge

Answer 2

V= W/ Q

Question 3

Ohms Law

Answer 3

Current and voltage are directly proportional

Question 4

In a circuit was is used up and what is conserved between voltage and current

Answer 4

voltage is used up and current is conserved as well as charge

Question 5

Conductor band width

Answer 5

Band gap between the valence band and conductor band is small. So many electrons travel through the conduction band

Question 6

Semi Conductor band width

Answer 6

Band gap is larger so only few electrons reach the conduction band

Question 7

Insulator band width

Answer 7

Does not conduct electricity so no electrons can reach the conduction band

Question 8

Superconductors characteristics

Answer 8

Zero resistivity at and below the critical transition temperature (-260 degrees)

Question 9

Equation for resistivity

Answer 9

resistivity= RA/ L

Question 10

3 equations for power involving current, resistance and voltage

Answer 10

P= VI
P= I^2 R
P= V^2 / R

Question 11

KIrchoff’s 1st law

Answer 11

At any junction in a circuit the sum of currents flowing in is equal to the sum of currents flowing out (conservation of charge)

Question 12

Kirchoff’s 2nd law

Answer 12

For any closed loop in a circuit the sum of emf is equal to the sum of the potential difference (conservation of energy)

Question 13

Examples of potential dividers

Answer 13

Thermistor
LDR
Variable resistor

Question 14

Equation for potential energy of an electron

Answer 14

0.5mv^2

Question 15

2 equations to calculate EMF
(r is internal resistance)

Answer 15

E= IR + Ir
E= I(R+r)

Question 16

What is electromotive force

Answer 16

Is the work done on the charge carriers per unit charge measured across the power supply

Question 17

3 equations for energy transferred

Answer 17

W= IVt
W= Pt
W= VQ

Question 18

Resistivity of a metal when temperature increases

Answer 18

Increasing the temperature causes the electrons vibrations to increase in amplitude, therefore the distnace it travels before another collision decreases. Resistivity increases with increasing temperature