Formulae

Question 1

Current (amperes)

Answer 1

Current (amperes) = charge (coulombs) passing a point per second.

I = Q/T

Question 2

Rearrange the formula I = Q/t (electric current) so that Q (charge) is the subject.

Answer 2

Q= I × t

Question 3

Resistance at constant temperature

Answer 3

Resistance (Ohms) = potential difference (Volts)/current (Amperes)

R = V/I

Question 4

Power in a circuit

Answer 4

Power (watts) = potential difference (volts) × current (amperes).

Power = VI

Question 5

Energy transformed in a circuit

Answer 5

Energy = power × time so:

Energy transformed in a circuit = potential difference (V) × current (A) × time (s)

E = VIt

Question 6

Distance =

Answer 6

Distance = rate × time

D = rt

Question 7

Density =

Answer 7

Density = mass divided by volume

D= m/v

Question 8

Average speed =

Answer 8

Average speed = distance moved divided by time taken

avg speed = distance/ time

Question 9

Relative density =

Answer 9

Relative density = density of substance/density of water

Question 10

Average acceleration =

Answer 10

Average acceleration = change in velocity/time taken

Question 11

Slope =

Answer 11

rise/run

Question 12

Pressure=

Answer 12

weight/area

Question 13

At depth h in liquid of density d:

Answer 13

pressure = pgh

Question 14

Work done =

Answer 14

force × distance

Question 15

1 volt =

Answer 15

1 J/C

1 Joule per Coulomb

Question 16

What is the equation for the momentum of an object?

Answer 16

mass × velocity

Question 17

Force linked to change in momentum

Answer 17

F=(mv-mu)/t

Force = change in momentum / time taken

Question 18

Pressure and volume in a gas

Answer 18

PV = constant

Pressure × volume = constant

Question 19

Kinetic energy (KE) =

Answer 19

KE = 1/2mv²

Question 20

Refractive index=

Answer 20

Refractive index= speed of light in air/speed of light in medium

Question 21

Critical angle

Answer 21

sin c = 1/n

c= critical angle
n= refractive index (of medium)

Question 22

Electrical power

Answer 22

P = IV

I = current
V = e.m.f or voltage

Question 23

The equation linking force, mass and acceleration

Answer 23

F= m×a

Question 24

Boyle’s law (compressing gases)

Answer 24

p1v1 = p2v2

Question 25

Wave equation

Answer 25

speed = frequency × wavelength

Question 26

Refractive index

Answer 26

Speed of light in vacuum ÷ speed of light in medium

or

Sin i ÷ sin r