Qualification > Reference Material

Physics P3 27/5/2010

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dodi23:
Thanks man!!
ill +rep u in an hour ;)

J.Darren:
There's gonna be a neutral point between like charges and magnetic poles :D

CONVENTIONAL CURRENT
Direction of + to - is the same as - to +.

Switches
Transistor can also act as switch.

Difference between EMF and PD

EMF - supplied to the whole circuit.
PD - across a component in the circuit.

CHARGE BY INDUCTION
Towards the very end you should point your finger at the object to compensate for the electron gone in the object (as the object is positively charged at the instance).

DC / AC MOTOR

In DC motor the current is responsible for the turning effect. Whereas in AC you turn the handle manually to induce current.

Using a stronger metal, make the area of the coil larger, increase the number of turns and stronger current (DC) would enhance the output of the motor.

Also a commutator and carbon brush is needed to enable the wire overshoots each other so that the coil can keep on turning.

POWER DISSIPATED

Particularly useful when you are required to measure the power loss in a transmission cable.

I^2 R

SNAIL'S LAW

If you are measuring from a denser to a rarer medium, take the reciprocal of the formula, i.e. (sin r / sin i), bear in mind the the refracted angle must be larger than incidence angle in this case.

WARRIOR:
lol thanks ill use those when i get to them

+ rep for now :P

J.Darren:
Thanks in advance :D

GRAVITATIONAL PULL

An object with greater volume would encouter more air resistance.

PRESSURE

Force / Area

10 x Density x Depth from surface

Atmospheric pressure - present at all times, 1 x 10^5, a classic question would require you to work out the pressure when at the surface of sea water and when it is few metres below sea level, be sure to include it in your calculation :D

THERMISTOR

As the temperature increases, the resistance in the thermistor decreases. It is a definiton, as thermistor is made up of semi-conductors.

The lower part of the circuit gets more share of the resistance (note that this part must NOT be connected to a transistor), more current can then flow through it, thus switching on the lamp.

LDR

As the light intensity decreases, the resistance increases.

The part of the circuit with the LDR gets more share of the resistance (note that this part must be connected to a transistor), more current can then flow through it, thus switching on the lamp.

THERMOCOUPLE

Consists of a copper wire, Constantan wire, a hot junction, a cold junction and a digital meter. Due to temperature difference there would be a current flow between the two wires. The greater the temperature differnce, the greater the current. The digital meter converts the current reading into temperature.

MOMENT

The meter rule would only be at equlibrium if net moment = 0 and the experiment obeys the principle of moment.

WAVES

Frequency of the same wave would always be the same, only the wavelength would differ depending on the medium of which it travels in.

Transverse - Particles vibrate perpendicularly to the direction of which the wave travels in.

Longitituional - Particles vibrate in the same direction of which the wave travels in.

BROWNIAN MOTION

Dust particles would randomly collide with air particles, they get suspended in the air. If there is an increase in temperature, Brownian Motion would slow down.

ADVANTAGES OF CONNECTING LAMPS IN PARALLEL

- Even if one lamp goes out, the other remains unaffected as the parallel circuit is still complete.
- Both lamps would glow at normal brightness (i.e. receives full PD from the power supply).

CENTRIPEDAL / CENTRIFUGAL FORCE

Centripedal - the force that is keeping an object in a circular track.

Centrifugal - the force that intends to throw an object off a circular track.

More centripedal force would be needed if the velocity / mass of the object increases.

CONDUCTION

Energetic particles would travel from a hot junction to a cold junction in a material.

HOOKE'S LAW

Force applied is directly proportional to the extension of the spring.

The point when the graph starts to bend is called the extension limit.

The line might break is more force is applied when the spring has already reached the extension limit.

J.Darren:
TERMINAL VELOCITY

When gravitational pull = air resistance, net force = 0. An object experiencing more resistance would reach terminal velocity faster assuming that the object that it is being compared to has the same mass.

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