GCSE Physics Required practicals

Required Practical 1 - Practical that can be used to determine the specific heat capacity of a material

• Place beaker on balance and press zero

• Add oil to beaker and record mass of the oil

• Place thermometer and immersion heater in oil

• Read starting temperature of oil

• Wrap the beaker in insulation foam to reduce thermal energy transfer to the surroundings

• Connect a joulemeter and power pack to the immersion heater

• Time set for thirty minutes

• Read the number of joules of energy that passed into the immersion heater

• Read final temperature of the oil

Equation for Specific Heat capacity

c = Change in E / m x Change in Temp

How to find specific heat capacity from the experiment results

• Use mass of oil

• Change in temperature (e.g: 20C to 75C = 55C change)

• Use energy from Joulemeter reading

• Plug into equation

What are the sources in inaccuracy in RP 1 and solutions?

Thermal energy passing out of the beaker into the air - Use an insulator with a lower thermal conductivity

Not all thermal energy passing into the oil - ensure that immersion heater is fully submerged

Incorrect reading of thermometer - Use an electronic temperature prone

Thermal energy not being spread through oil - stir the oil

Required Practical 2 - How to investigate the effectiveness of thermal insulators

• Place small beaker inside larger beaker

• Use a kettle to boil some water

• Transfer 80cm3 of hot water into the small beaker

• Use a piece of cardboard as a lid for the large beaker

• Lid must have a hole for a thermometer

• Place thermometer through hole and the bulb of the thermometer must be in the hot water

• Record starting temperature and start the stopwatch

• Need to record the temperature of the water every three minutes for fifteen minutes

• Repeat the experiment using the same volume of hot water - use insulating material like bubble wrap to fill the gap between two beakers - test range of different material (cotton wool or polystyrene balls)

• Same mass of material to be used each time

• Starting temperature of water should be the same

• Results can be plotted in table and cooling curve can be drawn for each insulator

• Water cools down most slowly - most effective material

Determining the effectiveness of thickness of thermal material

• Beaker containing 80cm3 of hot water

• Measure temperature of the water every three minutes for fifteen minutes

• Repeat the experiment with two layers of newspaper wrapped around beaker

• Repeat experiment 2 more times with 4 then 6 layers of newspaper

• More layers - more effective insulators

Required Practical 3 - Describe how to investigate the factors affecting the resistance of electrical circuits

• Attach wire to a metre ruler using tape

• Connect the wire using two crocodile clips to the rest of the circuits

• Crocodile clips can be moved further apart to increase length of wire in the circuit (can measure resistance based on length of wire)

• Ammeter, battery, and voltmeter used in rest of the circuit - can be used to determine resistance R = V/I

• Graph used - straight line which passes through 0 - resistance of wire is directly proportional to length of wire

What is a zero error

Reading on a measuring instrument when the value should be 0

Systematic error - cannot reduce it by carrying out repeats

In case of resistance - we need to subtract the zero error from all of our readings

Caused by crocodile clips which are not exactly at 0 on ruler

Heating effects on Resistance and solution

If temperature of wire increases, resistance increases, affecting results
So use low Potential different to keep current low, reducing heat of wire
Only turn on current when taking reading, turn off between readings

What is a variable resistor?

Can be used by moving slider to change length of coil of wire

Required Practical 4: I / V Characteristics

• Batteries connected by wires to resistor, with resistor in series with ammeter and a variable resistor

• Voltmeter in parallel across resistor

• Use voltmeter to read the potential different across the resistor

• Use ammeter to read the current through the resistor

• Record values in table

• Adjust the variable resistor and record new readings on the voltmeter and ammeter

• Several times to get a range of reading

• Switch direction of battery so that the direction of the potential difference has now reversed

• Both voltmeter and ammeter should now have negative values

• Continue taking several readings of potential different and currents

• Plot graph of current vs PD - Straight line passing through 0

• Current through a resistor is directly proportional to the potential difference - resistor ohmic conductor

• Change direction - still straight line passing through 0

• Temperature of resistor stays constant

• Important to not leave circuit connected for to o long

Repeat experiment with filament lamp and diode

Required practical 5 - Determine density of regular and irregular solids

Regular - Find volume and measure mass to find density

Irregular - Fill eureka can with water, add irregular object and measure the volume of water that comes out of the eureka can - that is the volume. Measure the mass with a weighing scale

Use equation Density = Mass/Volume

Required Practical 6 - Stretching a string

• Clamp stand, two bosses and two clamps

• Place heavy weight on clamp stand to stop it from falling over

• Attach metre rule and spring

• Top of spring must be at the zero point on the metre rule

• The meter rule must be vertical otherwise the readings will be inaccurate

• Bottom of spring has a wooden splint attached as a pointer

• This pointer must be horizontal or readings will be inaccurate

• Read position of this pointer on the metre rule

• This is the unstretched length of the spring - length no force attached

• Add 1 Newton weight on spring - read new position of pointer

• Repeat

• Work out extension produced from each weight - subtract unstretched length from each reading

• Plot extension against weight - straight line going through origin - extension is directly proportional to weight

• When there is too much weight - spring overstretched - inelastic deformation - exceeded the limit of proportionality

Required Practical 7 - Acceleration

• Toy car attached to a piece of string which is looped around a pulley

• 100g mass on the end of the string, the weight of the mass will provide the force acting on the toy car

• Chalk lines at equal interval and hold the toy car at the starting point

• Let go of car and car will accelerate along bench due to resultant force

• Record time that car passes each distant marker (phone can be used to get times accurately if car is moving fast)

• Repeat experiment, each case decrease mass on the end of the string but transfer the mass taken away onto the toy car to keep object mass the same

• Acceleration of the toy car is proportional to the mass on the other end of the string

• Experiment can be done the other way by increasing mass of the object while keeping force the same

• As we increase the mass of the toy car, the acceleration decreases

Required Practical 8: Waves in a solid

• String on one end attached to vibration generator and at the other end of string hanging mass

• Mass keeps string taut

• Vibration generator attached to signal generator allowing us to change the frequency of vibration of the string

• When power turns on string, vibration

• Standing wave and measure wavelength of it using ruler - total length from wooden ridge to the vibration generator

• Use length to calculate speed of the wave (read frequency from signal generator)

• To calculate wavelength, divide total length by number of half wavelengths then multiply by two

Required Practical 9: Reflection and Refraction

• Ray box, lens and slit produces a narrow ray of light

• Piece of A3 paper - draw straight line down centre and use protractor to draw a line at right angle - this is the normal (N)

• Place glass block against first line so normal in the centre of glass block

• Draw line around glass block

• Turn off lights in room and use ray block so it hits the glass block at the normal (incident ray)

• Angle of incidence is the angle between incident ray and normal

• Adjust ray box to change the angle of incidence

• At a certain angle, ray reflects from from surface of block

• Another ray is seen leaving the block from the opposite side - transmitted ray

• Mark path of incident ray and the reflected ray with crosses (and transmitted ray)

• Draw in the rays

• Draw line to show path of transmitted ray through glass block

• Measure both the angle of incidence and the angle of reflection and angle of refraction

• Repeat with a different block material

• Angle of incidence and reflection are same even due to material but angle of refraction will be different

Required Practical 10: Infrared emission

• Leslie’s cube used to see how much infrared is emitted from different surfaces

• Has four different surfaces (shiny metallic, white, shiny black, matte black)

• Fill Leslie’s cube with hot water

• Point infrared detector at each of the four surfaces and record the amount of infrared emitted

• Keep distance between the infrared detector and Leslie cube the same (repeatable measurement)

• Matt black surface emits most infrared radiation and shiny metallic, least amount of infrared radiation

Required Practical 10: Infrared absorption

• Infrared heater and on either side two metal plates

• One plate painted with shiny metallic paint and the other with matte black paint

• On other side vaseline is used to attach drawing pin

• Switch on the heater and start timing, temperature of metal plates increases at they absorb infrared

• Record time it takes for vaseline to metl and drawing pin to fall off

• vaseline on matt black surface melts first - infrared is better absorbed and emitted

• Infrared tends to be reflected from shiny metallic surfaces