FORMULA/DEFINITION SEMESTER 2

Stpm Physics Sem 2 Definition List

STPM Physics Semester 2 – Definition

Chapter 12 Definition Formula
No Term
1 Coulomb’s law The magnitude of electric force between two-point F = Qq
charges is directly proportional to the product of the two 4 0 r 2
charges and inversely proportional to the square of
distance between the charges

2 Electric field A region in which an electric charge experiences an
electrostatic force

3 Electric field The electric force per unit positive charge E = F = Q
strength at a q 4 0 r 2
point
E=V
d

4 Gauss’s law The net electric flux passing through a closed surface is  = Q
equal to the total net charge, Q inside the closed surface
divided by the permittivity of the medium 0
 = EA
 = Q

0

 = Total electric flux through a closed surface

Q = Algebraic sum of charged in a closed surface

0 = Permittivity of free space

5 Electric potential Work done in bringing a unit positive charge from V =W = Q
q 40r
at a point infinity to that point

6 Electric potential Work done in bringing the charge from infinity to that U = qV = Qq
4 0 r
energy point

7 Equipotential Line where the electric potential at every point on the
line line are the same

8 Equipotential Surface where the electric potential at every point on the
surface surface are the same

9 Equipotential Volume where the electric potential at every point on the
volume volume are the same

1

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PN NOURUL SARAH BINTI ZAINUDDIN

Chapter 13

No Term Definition Formula
C=Q
1 Capacitance of Ratio of charge on the capacitor to the potential
capacitor difference across the capacitor V
C = Capacitance of capacitor

Q = Charge on either plate of the capacitor

V = Potential difference across the plates

2 Dielectric Insulating material which is inserted between the C = 0 A C = 0r A
two plates of a capacitor dd

3 Capacitors in V1 =Q V2 =Q V3 =Q
series C1 C2 C3

4 Capacitors in 1=1+ 1 +1
parallel C C1 C2 C3

V = V1 +V2 +V3

Q = Q1 = Q2 = Q3

Q1 = C1V Q2 = C2V Q3 = C3V

Q = Q1 + Q2 + Q3

C = C1 + C2 + C3

V = V1 = V2 = V3

5 Energy stored U = 1 QV = 1 Q2 = 1 CV 2
in Capacitor 2 2C 2

6 Charging  t
Capacitor Q = Q0 1− eCR 
through a
Resistor 
 t
7 Discharging V = V0 1− eCR 
Capacitor 
through a
Resistor t

I = I0eCR

t

Q = Q0eCR

t

V = V0eCR

t

I = I0eCR

2

PREPARED BY
PN NOURUL SARAH BINTI ZAINUDDIN

Chapter 14 Definition Formula
No Term Electrons that are not attached to the atoms, and
1 Free electrons are free to move in an electric field I = dQ
dt
2 Electric current Rate of flow of charge

3 Drift velocity Drift velocity is the average velocity of free electrons vd = I
in a conductor when an electric field is applied along nAe
the conductor.

4 Current density Average velocity that causes a net flow of charge and J = I = nAvd e = nvd e
5 Ohm’s law produces a current in a conductor A A

6 Resistance The electric current per unit area of the cross- R=V
section I

The electric current flowing through a conductor is
directly proportional to the potential difference
across the conductor provided temperature
remains constant

The potential difference of conductor divided by
current flowing through the conductor

7 Conductance The opposition to the flow of an a.c. current or a d.c.  = RA = 1
8 Resistivity current. l
Reciprocal of resistance
9 Conductivity  = J = ne2t
The resistance per unit length of the material when Em
its cross-sectional area is 1m2

Reciprocal of resistivity

10 Mean free time The average time between two collisions of a free
11 Mean free path electron with the lattice atoms
12 Superconductor
The average distance travelled by a free electron
13 Critical between two collisions
temperature
A substance that will conduct electricity without
resistance or zero resistance at sufficiently low
temperature

The temperature at which the resistance of
substance became zero

3

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PN NOURUL SARAH BINTI ZAINUDDIN

Chapter 15 Definition Formula

No Term Direct current is a current that flows only in one
1 Direct current direction.

2 Potential The work done per unit charge between the two
difference points
between/across
two points

3 Electromotive The amount of electric potential given to one I =0
force (e.m.f) of a coulomb of charge, when the one coulomb of
battery charge flows through the battery and then around
a loop in the circuit
4 Kirchhoff’s first
law/ Kirchhoff’s The algebraic sum of current entering a junction in
current law a circuit is equal to zero

5 Kirchhoff’s second The algebraic sum of the changes in electric  E = V = (IR)

law/ Kirchhoff’s potential around a closed loop in a circuit is equal

voltage law to zero

6 Potential divider A linear circuit used to produce an output voltage V1 = R1 V
7 Shunt which is a fraction of an input voltage RT
8 Multiplier
A resistor which is connected in parallel with the V = VmilliammeterShunt
9 Potentiometer coil of a moving coil meter to convert the meter
from a milliammeter to an ammeter, so that the V = V + Vmilliammeter Multiplier
meter can measure a higher current
V Rl
A high resistance resistor which is connected in
series with the coil of a moving coil meter to
convert the meter from a milliammeter to a
voltmeter so that the meter can measure a higher
voltage

Used to measure the potential difference or
voltage, e.m.f and to compare two voltages

4

PREPARED BY
PN NOURUL SARAH BINTI ZAINUDDIN

Chapter 16

No Term Definition Formula

1 Magnetic B = Magnetic field F = q ( B  v) = qvB sin
Force F = Magnetic Force acting on the charge
B= F
q = Magnitude of the positve charge qv sin

v = Velocity of the charge F = IlBsin

 = Angle between the velocity and magnetic flux density, B  Blll = 0I

2 Magnetic field A region in space in which a magnetic force can act on a
moving charged particle

3 Magnetic flux Force per unit charge acting on a charged particle

density moving at 1 ms-1, at the right angle to the magnetic

field

4 Magnetic
Force on a
straight
current-
carrying
conductor

5 Ampere’s law The sum of the products B and Δl over a closed loop is
equal to the product of current through the loop and
permeability of free space

In a closed loop, sum of the “Length elements x the
magnetic field in the direction of the length element” =
Permeability x the electric current in the loop.

6 Magnetic Field B = 0NI
of a straight 2r
wire
B = 0I
7 Magnetic Field 2 d
for a Circular
Coil B = 0nI

8 Magnetic Field
for a Solenoid

9 Force F = 0I1I2
between two l 2 d
parallel
current-
carrying
conductors

5

PREPARED BY
PN NOURUL SARAH BINTI ZAINUDDIN

10 Determination e = E2 = E = 2V
of the ratio m 2B2V B2r B2r 2
e/m for
electrons in VH = BI
Thomson’s net
experiment

11 Hall effect

v= E
B

Chapter 17 Definition Formula
= B•A
No Term Equal to the dot product of magnetic flux
1 Magnetic flux density vector and area vector  = −N d
dt
2 Magnetic flux If a coil has N turns of wire and an area, A and
linkage the magnetic field B is perpendicular to the
plane of coil
3 Magnetic flux The number of magnetic field lines per unit
density area perpendicular to vector

4 Faraday’s law The induced e.m.f produced in a coil is directly
proportional to the rate of change of magnetic
flux linkage of the coil

5 Lenz’s law The induced current will flow in a direction
such that the magnetic field produced by the
6 Generator induced current will always oppose the
Dynamo changing magnetic flux that produces the
induced current
7 Linear
Conductor The direction of the current induced is to
produce a force to oppose the change of
magnetic flux (that causes it)

 = N d = NBA d (sint )

dt dt
 = NBAcost

 = Blv

6

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PN NOURUL SARAH BINTI ZAINUDDIN

8 Self-induction in When the current in the coil changes, there is an

a coil induced e.m.f produced in the same coil

Self induction is the production of an induced L = 
e.m.f. in a coil due to the changing current in the dI
same coil.
dt
9 Self-inductance Equal the induced e.m.f produced in the coil LI = N
divided by the rate of change of current in the L = 0N 2 A
same coil
l

10 Energy stored U = 1 LI 2
inn an inductor 2

11 Mutual induction When the current in coil 1 changes, there is an
induced e.m.f produced in coil 2

12 Mutual Equal to the induced e.m.f in the secondary coil M = 
inductance divided by the rate of change of the current in dI
the primary coil
dt

MI1 = N22
M = 0N p NS A

lP

Chapter 18 Definition Formula

No Term A current in which the direction of the
1 Alternating current changes or reverses periodically

current

2 Direct current A current in which the direction of current is Irms = I0
3 r.m.s. voltage always the same 2

r.m.s. voltage is equal to the direct current Vrms = V0
voltage which canproduce the same heating 2
power as the mean power of the a.c. supply in
the same resistor.

4 Root-mean Value of a constant direct current which can

square value of produce the same heating power as the

a.c. alternating current in a given resistor

5 Phasor A vector of constant magnitude and rotating
in an anticlockwise direction with a constant
angular velocity

7

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6 A pure resistor V = V0 sin t
I = I0 sin t
P = VI

P = (V0 sin t )( I0 sin t )

P = V0I0 sin2 t

P = V0I0 = 2Vrms Irms = I 02 R = V02
R

7 A pure inductor V = V0 sin t

I = −I0 cost

P = V0I0 sin 2t = V0I0 = Vrms Irms
2 2

8 A pure capacitor V = V0 sin t

I = I0 cost

P = V0I0 sin 2t = V0I0 = Vrms Irms
2 2

9 Reactance Opposition to the current by an inductor or XL = L = 2 fL = V0 = Vrms
a capacitor in an a.c. Circuit I0 I rms

XC = 1 = 1 = V0 = Vrms
C 2 fC I0 I rms

6 Impedance Vector sum of the resistance and the Z = R2 + ( X L − XC )2
reactance in an a.c. Circuit

Impedance is the opposition to an
alternating current due to resistance and
reactance.

8

PREPARED BY
PN NOURUL SARAH BINTI ZAINUDDIN