Chapter 12,13 Equations

Question 1

Charge
Current
Time

Answer 1

Current = i = ΔQ÷ΔT 
Charge = Q = i x ΔT

Question 2

Power ( with time)

Answer 2

Energy / time

i x v x ΔT / ΔT = i x v

Question 3

Electrical power

Answer 3

P = i x v

Question 4

Pd

Answer 4

P.d. = V = W/Q
Work done = W = Q x V
Charge = Q = W/V

Question 5

Resistance / power / current

Answer 5

V = I x R
R = v/i 
I = V/R

Question 6

Resistance

Answer 6

R = P x l / A

R = resistance (Ω)
P = Resistivity (Ωm)
L = length (Ωm²/m)
A = cross sectional area (m²) = Ωm

Question 7

Resistivity

Answer 7

P = R x A / L

Question 8

Current / pd / resistance

Answer 8

Pd / c = res
Res x c = pd
Pd/res = current

Question 9

In series

Answer 9

V = v1 + v2

RT = R1+R2+R3

Question 10

In parallel

Answer 10

i = i1 +i2

1/RT = 1/R1 + 1/R2

Question 11

Power

Answer 11

P = i x v
P = i² x v
P = v²/R

Question 12

EMF

Answer 12

ε = E/Q 
E = energy 
Q = charge 
ε = emf

Question 13

Pd across a cell

Answer 13

V = ε - (i x r)

```
i x r) = pd used in internal resistance (v=ixr
V = pd
ε = emf
i = current
r = resistivity
~~~

Question 14

Cell emf

Answer 14

ε = i x R + i x r

ε = emf 
i = current 
R = resistance 
r = internal resistance

Question 15

Booklet emf

Answer 15

E = i x (R + r)
E = energy 
i = current 
R = resistance 
r = resistivity

Question 16

Current with emf

Answer 16

i = ε / R + r

Question 17

Internal resistance

Answer 17

r = v1 - v2 / i2 - i1