phys u2

Current

Rate of flow of charge

Current symbol

I

Current formula

I=ΔQ/Δt

Q=It

I = Q/t

Current SI (base) unit

A

Current: base quantity or derived quantity

Base quantity

Current:scalar or vector

Scalar quantity

Charge-time graph (Q-t) : gradient

Current —> I

Charge formula

Charge = current x time

Q = It

Charge: Si base unit

As

Charge SI unit

C

Charge: scalar or vector

Scalar quantity

Charge base or derived quantity

Derived

Area under I-t graph

—> charge

Quantisation of charge formula

Q= Ne

Q - total charge

N - no. of free electrons

e - charge of 1 e− e =0 1.6x10^-19C (basic charge)

Electrical component - cell

Electrical component - Battery

Electrical component - Dc power supply

Electrical component - Ac power supply

Electrical component - Variable power supply

Electrical component - Ammeter

Electrical component - Voltmeter

Electrical component - Ohmmeter

Electrical component - Variable resistor

Electrical component - LDR

Electrical component - Diode

Electrical component - LED

Electrical component - Fuse

Electrical component - Thermistor

Electrical component - Filament lamp

Electrical component - heater

Electrical component - One way switch

Electrical component - Two way switch

Electrical component - Potential divider

Potential difference

Work done per unit charge

Potential difference formula

V = w/Q

Potential difference SI unit

V (volt)

Potential difference SI base unit

Kgm^2s^-3A^-1

Potential difference scalar or vector quantity

Scalar

Potential difference base or derived quantity

Derived

Ohm’s law

Current through a metallic conductor is directly proportional to potential difference applied across it provided temperature and all the other physical quantities remain constant

Resistance definition

Ratio between voltage and current

Resistance formula

V=IR

R=V/I

R -> resistance

V -> voltage

I -> current

Resistance SI unit

Ω

Resistance scalar or vector

Scalar

Resistance base or derived

Derived

V-I graph gradient

R

I-v graph gradient

Gradient = 1/R

R = 1/gradient

Ohmic conductors and non-ohmic conductors: ohm’s law

Ohmic conductors: obeys ohm’s law

non-ohmic conductors: does not obey ohm’s law

Ohmic conductors and non-ohmic conductors: directly proportional or not proportional

Ohmic conductors: directly proportional

non-ohmic conductors: not directly proportional

Ohmic conductors and non-ohmic conductors: r constant or varies

Ohmic conductors: constant

non-ohmic conductors: varies

Ohmic conductors and non-ohmic conductors: I-v graph straight line or not straight line

Ohmic conductors: I-v graph is a straight line through origin

non-ohmic conductors: not a straight line

Ohmic conductors and non-ohmic conductors: Examples

Ohmic conductors: resistor

Metal wire at low temperature

non-ohmic conductor:

1. lamp

2. Thermistor

3. LDR

4. Diode

5. LED

Charge carrier density symbol

n

Charge carrier density formula

n = N/v

Charge carrier density unit:

m^-3

Charge carrier density: N

No. of free electrons

Charge carrier density: v

Volume

Charge carrier density

No. of free electrons per unit volume

Drift velocity symbol:

V

Drift velocity

Average/mean velocity of free e^- in a conductor when a p.d is applied across it

Drift veolcity si unit

Ms^-1

Drift velocity formula

V = I/naq

Kirchhoff’s 1st law/current law/Junction law

• Sum of currents entering a junction is equal to the sum of currents leaving out

• Net current at junction je zero

• Conservation of charge

Kirchhoff’s 2nd law

• supply voltage is equal to sum of individual voltage

• Net voltage around a close loop is zero

• Conservation of energy

Resistivity formula

𝜌 = RA/L

𝜌 - resistivity

R - resistance

A - cross sectional area

L - length

Resistivity si unit

Ωm

Resistivity

The resistance of a conductor/material of unit length of unit cross-sectional area of constant temp

I-v characteristics: resistor

I-v characteristics: Filament lamp

I-v characteristics: NTC thermistor

I-v characteristics: LDR

I-v characteristics: Diode or LED

emf formula

ε = v + Ir

ε in emf formula

emf

V in emf formula

Terminal p.d

Ir in emf formula

Lost volts

Emf

Work done in moving a charge around a circuit

Internal resistance

The resistance within the cell which opposed

Wave definition

Means of transferring energy

Type of waves

Mechanical waves

Electromagnetic waves

Mechanical and EM waves: medium

Mechanical: need medium

EM waves: do not need medium

Mechanical and EM waves: v

Mechanical: v varies

EM waves: v is constant

3x10^8

Mechanical and EM waves: eg

Mechanical: water waves, sound waves, waves along string, waves along spring

EM waves: radio, micro, light

Medium of propogration

Waves:

Transverse

Longitudinal

Transverse waves

Waves in which particles in the medium vibrate perpendicular to the direction of wave travel

Transverse eg

Waves along string

Surface water waves

Longitudinal waves

Waves in which particles in the medium vibrate parallel to the direction of wave travel

Longitudinal eg

Sound waves

Water waves beneath surface

Formula

V=f λ

Electromagnetic waves

Electromagnetic waves transfer energy through oscillations of electric and magnetic fields in perpendicular direction

Displacement-distance diagram

Displacement-time diagram

Em spectrum

Good eXplorers Underwater View Island Marine Reefs

EM spectrum: gamma

10^-12

EM spectrum: x-rays

10^-10

EM spectrum: UV

10^-8

EM spectrum: visible

10^-7

EM spectrum: IR

10^-6

EM spectrum: micro

10^-3/10^-2

Cooking/communication

EM spectrum: radio

1m -> 1km