M4C2

Question 1

What’s the formula for E.M.F.?

Answer 1

ε = E/Q
ε = E.M.F. (V)
E = energy transferred (J)
Q = charge (C)

Question 2

What’s the formula for P.D.?

Answer 2

V = W/Q
V = P.D. (V)
W = work done (J)
Q = charge (C)

Question 3

What is Ohm’s law?

Answer 3

The current through a conductor is directly proportional to the potential difference across it, provided that physical conditions, such as temperature, remain constant.

Question 4

What is the resistance equation?

Answer 4

R = V/I
R = resistance (Ω)
V = volts (V)
I = current (A)

Question 5

What’s the resistivity formula?

Answer 5

R = ρL/A
R = resistance (Ω)
ρ = resistivity (Ω m)
A = Area (m2)
L =  Length (m)

Question 6

How does temperature affect resistance?

Answer 6

The higher the temperature the higher the resistance

Question 7

What is the formula used to work out the effect of temperature on resistivity?

Answer 7

⍴T = ⍴0 [1 + α(T-T0)]
⍴T = resistivity of material at temperature T.
⍴0 = resistivity of material at T0 (usually room temperature).
α = temperature coefficient.
T = temperature of the material.
T0 = reference temperature at which the resistivity of the material is quoted (usually room temperature).

Question 8

Define resistivity

Answer 8

Resistivity is the amount of resistance per meter of a specific material

Question 9

What are the power equations?

Answer 9

P = VI
P = I^2R
P = V^2/R
P = power (W)
V = volts (V)
I = current (A)
R = resistance (Ω)

Question 10

How much energy does a 100 W bulb use if it’s left on for 10 hours?

a) in joules
b) in kwh

Answer 10

a)
E = Pt = 100 w x (10x60^2) s = 3,600,000 J
b)
E = Pt = 0.1 kw x 10 h = 1 kwh