knowledge test

Kinetic energy

the energy stored by particles or objects which are moving

Potential energy

the energy stored when particles or objects are interacting

Internal energy

the total amount of energy stored inside a system by the particles (kinetic energy + potential energy)

Temperature

A measure of the average kinetic energy of particles

Specific heat capacity

the energy required to raise the temperature of 1 kg of a substance by 1°C

Specific latent heat

the amount of energy required to change the state of 1 kg of a substance with no change in temperature

where does kinetic energy occur in the substance

in the atoms

where does potential difference occur in the substance

in the bonds

potential difference

how much energy is transferred to or from the charges as they pass through a component

SHC unit

J/kgK

SLH unit

J/kg

what is Kelvin

a temperature scale where zero reflects the complete absence of thermal energy

Determining the s.l.h of fusion

1. Place 2 beaker on separate balances then zero the scale. 

2. Clamp a funnel above each beaker. 

3. Connect immersion heater to power source. 

4. Add ammeter in series and voltmeter in parallel. 

5. Place immersion heater in one of the funnels. 

6. Add 70g of ice to each funnel. 

7. Turn on immersion heater and start stopwatch. 

8. Record the potential difference and current. 

9. After suitable period of time remove funnels, stop the stop watch and turn off heater. 

10. Record the mass of water in the beaker.

Determining the s.l.h of vapourisation

1. Place the immersion heater into the fluid contained in the conical flask

2. Connect the immersion heater to the power supply.

3. Add an ammeter in series and a voltmeter in parallel with the heater

4. Turn on the immersion heater and start the stopwatch

5. Record the potential difference and current at regular time intervals.

6. After a suitable period of time, turn off the immersion heater and stop the stopwatch

7. Record the mass of the fluid remaining in the conical flask.

Current

how much charge (electrons) flows each second

Energy

the ability to do work (transfer from one store to another)

Power

how much energy is transferred per second

Charge unit

Coulombs, C

Power unit

Watts, W

Energy transferred unit

Joules, J

Potential difference unit

Volts, V

Current unit

Amps, A

Resistance unit

Ohms, Ω

How do you calibrate a voltmeter?

1. Connect power pack to the mains.

2. Connect power pack to the voltmeter.

3. Connect voltmeter to the top of resistor.

4. Connect the bottoms of the resistor to the power pack.

5. Set up the multimeter with the cables in correct ports.

6. Connect the multimeter from the power pack to the top of the resistor.

7. Take note of the readings.

ohms law

Potential difference is directly proportional to current and resistance

Resistivity

A measure of how strongly a material resists electrical current

Random error

occur in every measurement and cant be removed

only way to deal with them is to take repeat measurements and calculate average.

Systematic error

occur because there is a problem with the equipment or method

Accuracy

how close the measured value is the true value

Precision

how reproducible the results are

what if the readings are not the same (calib)

note down the difference between the reading on the collaborated device and component. add or minus this value from any readings you make on ammeter or voltmeter

Thermistor function

changes resistance dependent on the temperature of its surroundings

LDR function

changes resistance dependent on the brightness of its surroundings.

Diode function

only allows current to flow in one direction

Photodiode

converts light to electrical current

If i place a diode in forward bias what happens

Low Resistance - High Current (steep gradient)

if i place a diode in reverse bias what happens

High Resistance - Almost no current (almost flat gradient)

what happens to resistance when there’s a present thermistor

Resistance decreases if the temperature increases.

what happens to resistance when there’s a present LDR

Resistance decreases if the light intensity increases.

Example of thermistor

fire alarm

Example of LDR

street lights

filament lamp example 

vintage lighting

led example 

traffic lights, screens

diode example

Converting AC to DC

photodiode example

remote controls, solar panels