Electricity

Question 1

Current

Answer 1

(A)
charge (C)
—————–
time (s)

I = Q
—
t

Question 2

Voltage

Answer 2

(V)
energy transferred (J)
———————————
charge (C)

V = E
—
Q

Question 3

Voltage

Answer 3

(V)
current (A) × resistance (Ω)

V = IR

Question 4

Power

Answer 4

(W)
current (A) × voltage (V)

P = IV

Question 5

resistance

Answer 5

resistance (Ω) = Power (W)
—————
current^2
R= P(W)
——–
I^2

Question 6

Energy transferred (J)

Answer 6

(J)
current (A) × voltage (V) × time (s)

ΔE = IVt

Question 7

Energy transferred

Answer 7

(J)
power (W) × time (s)

ΔE = Pt

Question 8

Resistors in series

Answer 8

Total Resistance (Ω) = sum of individual resistors (Ω) RTOTAL = R1+R2+R3+…Rn

Question 9

Resistors in parallel

Answer 9

          total resistance (Ω) 
                           =
                            1 ----------------------------------------------------
 sum of individual resistors (Ω)

1 1 + 1 + 1
– = — — —
Rt R1 R2 R3

Question 10

Resistance

Answer 10

(Ω)
resistivity (Ωm) × length (m)
—————————————-
area (m2)

R = ρl
—-
A

Note: since wires have a circular cross section, area = π × radius2

Question 11

Transformers

Answer 11

voltage in primary coil (V)
=
turns on secondary coil
———————————-
turns on primary coil

Vs Ns
—- =
Vp Np

Question 12

Transformers

Answer 12

voltage in secondary coil
=
current in secondary coil (A)
—————————————–
current in primary coil (A)

Vp Is
—- = —-
Vs Ip