PAGS

Question 1

Method determining gravity

Answer 1

• Set up an electromagnet with a low voltage DC supply onto a clamp stand
• Connect one light gate and data logger as close to the electromagnet as possible, and one at 0.75m
• Turn on the electromagnet and attach a ball bearing
• Switch off the electromagnet and time how long it takes for the bearing to fall between the light gates
• Adjust the height of the lower light gate by moving it up 0.05m each time until it reached 0.25m
• find the mean values of t for each value of h
• plot a graph of 2h against t² so the gradient will equal g (s = ut+1/2at²)

Question 2

Investigating terminal velocity

Answer 2

• Wrap elastic bands around a cylinder of viscous liquid at set intervals measured by a ruler
• Drop a ball bearing into the tube and record the time it takes to reach each band
• Repeat the method to reduce the effect of random errors and use a strong magnet to remove the ball bearing from the bottom of the tube
• Calculate the average time taken for the ball to travel between each consecutive band
• Use the equation S=d/t to find the average velocity between each band
• Plot a graph of velocity against time
• Terminal velocity can be identified when the ball takes an equal amount of time to travel between the bands

Question 3

Investigating springs in series and parallel

Answer 3

• Set up a clamp stand attached to (n) springs in series/parallel attached to a 50g mass
• Record the initial length of the springs and the number of springs in series or parallel (n)
• Attach the mass and record the new length of the springs
• Repeat with different values of n
• Calculate the extension for each spring (new length-initial length)
• Find the spring constant of the combination (Force/extension of n)
• Total extension = sum of each individual springs extension

Question 4

Determining resistivity

Answer 4

• Measured the diameter across three points using a micro meter and calculate the mean diameter
• Set up a power supply ammeter and voltmeter in parallel to the wire
• Attach crocodile clips along the length of the wire at 10 cm using a meter rule
• Read and record the current and volts
• Switch the circuit on and off in between readings to prevent heating of components
• Repeat this process by increasing the length by 10 cm every time until 80cm
• Repeat the experiment to increase reliability and calculate the mean resistance using V = IR
• Calculate the cross-sectional area of the wire using A = πd²/4
• Plot a graph of resistance against length, the resistivity will be the gradient x cross-sectional area

Question 5

Determining internal resistance

Answer 5

• Set up a circuit with a battery, ammeter, variable resistor, switch and voltmeter in parallel to the battery
• Set up the variable resistor to its maximum value
• Close the switch and record the voltage from the volt meter and the current from the ammeter
• Open the switch between readings to prevent heating
• Repeat this method decrease the resistance of the variable resistor each time
• Put the equation ε= V + Ir into the form y=mx+c and plot a graph of V against I
• y-intercept = emf and the gradient = negative internal resistance

Question 6

Using non-ohmic devices as sensors

Answer 6

• Set up a circuit with a cell connected to an LDR and voltmeter in parallel to resistor
• Record the value of light intensity using a digital light sensor
• Record the voltage across the resistor for the light intensity
• Using a lamp with a varying intensity increase the light intensity slightly and record the new value recorded by the sensor and record the voltage across the resistor
• Repeat this process until light intensity cannot be increased any further
• Plot a graph of voltage across the resistor and light intensity and draw a line of best fit