Physics GCSE

• What apparatus are needed to measure the specific heat capacity of a material?


  Power supply, joulemeter, heater, thermometer, material to test, insulation, stopclock, balance
• What measurements are taken in the specific heat capacity experiment, and what apparatus are used for each measurement?


  Measure the temperature of the material (with a thermometer) and the energy supplied to the heater (with a Joulemeter) every minute (with a stop clock) for 10 minutes. Measure the mass of the material (with a balance).
• Why is insulation used in the specific heat capacity experiment?

  To reduce energy transfer to the surroundings. This makes the specific heat capacity value more accurate.
• If insulation is not used in the specific heat capacity experiment, is the value of specific heat capacity too high or too low?

  Too high. This is because more of the energy transferred by the heater heats the surroundings compared to if insulation was used.
• What graph is plotted in the specific heat capacity experiment, and how is the graph used to find the specific heat capacity of the material?

  Plot temperature (y-axis) against energy supplied (x-axis). The straight bit of the graph is used to find the gradient. The specific heat capacity is then 1 ÷ (gradient x mass of the material).
• What apparatus are needed to investigate the effectiveness of thermal insulators?

  Thermal insulators, kettle, beaker, lid, stop clock, thermometer, funnel, heat proof mat, measuring cylinder.
• What measurements are taken in the thermal insulation practical, and what apparatus are used for each measurement?


  Measure 50 ml hot water from the kettle (with a measuring cylinder) and pour into the beaker. Measure the temperature of water in the beaker (with a thermometer) every minute (with a stop clock) for 10 minutes.
• What are two control variables in the thermal insulation practical?


  Same volume of water, same starting temperature.
• What is the hazard and risk, and what precautions are taken to reduce the risk in the thermal insulation practical?


  Hazard is the hot water, risk of spilt hot water causing burns, precaution is to use a funnel to pour hot water from the kettle and measuring cylinder.
• What graph is plotted in the thermal insulation practical, and how is it used to compare the effectiveness of different insulators?


  Plot temperature (y-axis) against time (x-axis). The smallest change in temperature in the same time is the best insulator.
• Draw or describe the circuit to measure potential difference (voltage) and current in all of the electricity practicals.


  Battery in series with an ammeter, variable resistor, switch and the component being tested. Voltmeter in parallel with the component being tested.

  
• What measurements are taken in the resistance of different wire lengths practical, and what apparatus are used for each measurement?


  Measure 10 cm length of wire (with a metre ruler), measure the potential difference across (with a voltmeter) and the current through (with an ammeter) the wire. Switch off. Repeat the measurements for 20, 30, 40, 50, 60 and 70 cm of wire. Use the measurements to calculate resistance.
• In electricity practicals what must happen between every measurement and why?


  The circuit must be switched off to reduce heating of the component. This is because changing the temperature of the component can effect its resistance.
• What are the control variables in the resistance of different wire lengths practical?


  Material of the wire, diameter of the wire, temperature of the wire.
• Work done (electrical)


  Energy transfer by charge flowing in a circuit.
• What graph is plotted in the resistance of different lengths of wire practical? What shape of graph do you expect, and what does this mean about the relationship between resistance and length?


  Plot resistance (y-axis) against length (x-axis). The graph should be a straight line through the origin. This shows that resistance is directly proportional to length.
• What is the hazard and risks, and what precautions are taken in electricity practicals?


  Hazard is high currents, risks are heating causing components/wires to melt or burns if touched. Precautions are to use low currents and switch off between measurements to reduce heating.
• Alternating potential difference


  A potential difference that is continually changing direction. It produces an alternating current (AC).
• What measurements are taken in the I-V graphs (characteristics) practical, and what apparatus are used to make each measurement?


  Adjust the variable resistor to produce a potential difference of 1 V (measured with a voltmeter) across the component being tested. Measure the current (with an ammeter). Switch off. Repeat the measurements for 2, 3, 4, and 5 V. Reverse the connections on the battery. Repeat the measurements for - 1, -2, -3, -4, -5 V.
• Ammeter


  Measures the current through a component. Connected in series.
• Why do you reverse the connections to the battery in the I-V graphs (characteristics) practical?


  To reverse the direction of the current through the component being tested.
• Ampere/Amp (A)


  The unit of current.
• For every measurement in a practical what should you do to reduce the effect of random error?

  Repeat the measurement twice and calculate a mean of the three measurements.
• Coulomb (C)


  The unit of charge flow.
• In the I-V graphs (characteristics) practical what shape graph should you get for a resistor at constant temperature and why?


  Straight line through the origin. Current is directly proportional to potential difference as an Ohmic resistor at constant temperature has a constant resistance.

  
• Current


  The rate of flow of charge. 1 Amp means 1 Coulomb of charge flow per second.
• In the I-V graphs (characteristics) practical what shape graph should you get for a filament lamp and why?

  Curve. ICITIR. Increasing the Current, Increases the Temperature, which Increases the Resistance.

  
• Diode


  Only allows current to flow through in one direction. Diodes have a very large resistance in the reverse direction.
• In the I-V graphs (characteristics) practical what shape graph should you get for a diode and why?


  Curve but only in the positive part of the graph. The diode has a very high resistance in the reverse direction. Current will only flow through a diode in one direction.

  
• Direct potential difference


  A potential difference that is always in the same direction. It produces a direct current (DC).
• In the parallel/series resistors practical, and resistance and length practical, how is resistance calculated from the measurements taken?

  Resistance = potential difference ÷ current
• Earth Wire


  ​The green and yellow striped safety wire at 0 V connected to metal casings, that prevents an appliance from becoming live.
• What measurements are taken in the parallel/series resistors practical, and what apparatus is used to take each measurement?

  Using a single resistor, use the variable resistor to produce a potential difference of 1 V (measured with a voltmeter) and measure the current (with an ammeter). Switch off. Repeat the measurements for 2, 3, and 4 identical resistors in series. Make sure the voltmeter is across all of the resistors being tested. Then repeat the measurements for 2, 3, and 4 identical resistors in parallel. Use the measurements to calculate resistance for each resistor combination.
• Electric field


  The area around a charged object that produces a non-contact force of either attraction or repulsion on other charged objects.
• Chemical Energy


  Energy found in things such as batteries, fuels and food.
• In the series/parallel resistors practical what graphs should you plot, what shape should they be, and why?


  Plot total circuit resistance (y-axis) against number of resistors (x-axis). Plot one graph for series resistors, the other for parallel. The series graph is a straight line showing that resistance is directly proportional to the number of resistors. The parallel graph is a curve showing that increasing the number of resistors, decreases the total resistance of the circuit.
• Filament lamp


  A lamp made of very thin piece of wire. Increasing current, increases temperature, increases resistance.
• Closed System


  A system that experiences no change in its total energy when energy transfers occur within it.
• What apparatus are used in all of the electricity practicals?

  Battery, switch, variable resistor, connecting wires, ammeter, voltmeter.
• Light Dependent Resistor (LDR)


  A light sensing component whose resistance decreases as the brightness of light increases.