Required Practicals Paper 1

Question 1

Specific heat capacity of a liquid experiment

Answer 1

• Tare a beaker on a mass balance and add add the liquid into the beaker and measure the mass of the liquid
• Place a heater and a thermometer into the liquid and record the starting temp
• Wrap in insulating foam to reduce energy transfer to surroundings
• Attach a joulemeter and a power pack to the heater so the energy input can be measured
• Leave for 30 mins and then read the final temp and the reading on the joulemeter

Question 2

Sources of error in the shc experiment and there fixes

Answer 2

• Thermal energy passing out of beaker - use good insulator (low thermal conductivity
• Incorrectly reading temp - use an electronic temperature probe
• Not all thermal energy from heater going into liquid - fully submerge heater

Question 3

How to investigate the I-V charcteristics of circuit components (common 6 marker)

Answer 3

• Use voltmeter to measure and read the p.d. across the resistor
• Use the ammeter to measure and read the current across the resistor
• Vary the resistance of the variable resistor
• Record the new values and do this several times to get a range of values
• Between tests open the switch to not keep the circuit connected
• This stops the temperature of the resistor from increasing
• Switch the direction of the battery to reverse the direction of the p.d.
• Again, take repeated readings of I and V but in the negative direction
• Plot a graph of current against p.d. (I-V Graph)
• If an ohmic conductor is used, p.d. and current are directly proportional in both forward and reverse directions

Question 4

What is different when investigating I and V characteristics of a diode

Answer 4

• Extra resistor - diodes are easily damaged by high current so keeps current low
• Sensitive ammeter is needed as a result so we use a milliammeter
• Current only after 0.6V and increase sharply after on I-V Graph
• No current in reverse direction as diodes have a high resistance in the reverse direction

Question 5

What is different when investigating I and V characteristics of a filament lamp

Answer 5

• I-V Graph is curved as I is not proportional to V
• This is because as the temp increases, the resistance also increases
• Same curved shape in reverse direction

Question 6

How to investigate the effect of thermal insulators

Answer 6

• Set up a can
• Pour boiling water from a kettle into the small one and add a lid and a thermometer and record the intial temp
• MEasure the temp change over time by recording the temp every 30 seconds
• Repeat but add an insulating material between the two beakers and use a range of insulating materials
• Plot cooling curves
• Higher temp at the end means a better insulator

Question 7

Variables in the thermal insulation experiment

Answer 7

• Independent - insulating material
• Dependent - temp change
• Control - volume of water, mass of insulating material

Question 8

How to find the resistance of the wire experiment

Answer 8

• Ammeter measures current in the circuit
• Voltmeter measures p.d across the wire
• Measure the length of the wire by attaching a wooden ruler to it using tape
• Vary the length of the wire using crocodile clips which means only the section of wire between the clips is part of the circuit and move the clips further apart
• Get a range of results by repeating and calculate the resistance for each length using R = V/I
• Plot a graph which will be directly proportional

Question 9

Issues regarding the resistance and length of the wire experiment

Answer 9

• There is a small resistance when the length is 0 - this is a zero error (systematic error) due to the crocodile clips having a resistance and not being at 0 on the ruler
• If the temp of the wire increases, the resistance also increases - use a low p.d. and turn off circuit when not taking readings

Question 10

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How to calculate the density of a regular and an irregular object

Answer 10

• Regular - find mass using a mass balance
• Find the volume by measuring the dimensions using a ruler or vernier callipers and multiplying them together
• Irregular - find mass by using a mass balance
• Fill eureka can with water until the water level is just below the spout
• gently lower the object in using a string and collect the water displaced in a measuring cylinder
• Volume of water displaced = volume of object
• To calculate density for both, you do ρ = m/v