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(a) Assemble the circuit of Fig. 1.1.
Make sure that the diode is connected the correct way round.
(b) Set the power supply voltage to 12V and close the switch.
Record the voltmeter reading $V$ and the ammeter reading $I$.
You should find that $I$ is at least 0.02A.
(c) Reduce the power supply voltage, recording $V$ and $I$ until you have six sets of readings.
Open the switch when you have finished your measurements.
Include in your table of results the values of $V^{10}$.
($V^{10}$ = $V \times V \times V \times V \times V \times V \times V \times V \times V \times V$)
(d) (i) Plot a graph of $I$ on the $y$-axis against $V^{10}$ on the $x$-axis.
(ii) Draw the straight line of best fit.
(iii) Determine the gradient and $y$-intercept of this line.
(e) It is suggested that the relationship between $I$ and $V$ is
$$I = aV^{10} + b$$
where $a$ and $b$ are constants.
Using your answers from (d)(iii), determine the values of $a$ and $b$. Give appropriate units.
594
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593
In this experiment, you will investigate how the speed of a glass ball falling through oil depends on its size.
The apparatus has been set out for you as shown in Fig. 2.1.
(a) Measure and record the distance x between the upper and lower marks on the measuring cylinder.
(b) (i) You have been provided with two different sizes of glass ball: large and small. Take measurements to determine the diameter d of the small glass balls.
(ii) Take measurements to determine the time t for a small glass ball to fall distance x through the oil.
Do not remove any balls from the oil. You may ask for more glass balls if needed.
(c) Estimate the percentage uncertainty in your value of t.
(d) Calculate the speed v of a small glass ball falling distance x through the oil.
$v = \frac{x}{t}$
(e) Repeat (b) and (d) for the large glass balls.
(f) It is suggested that the relationship between v and d is
$$v = kd^2$$
where $k$ is a constant.
(i) Using your data, calculate two values of $k$.
(ii) Explain whether your results support the suggested relationship.
(iii) Justify the number of significant figures that you have given for your values of $k$ in (i).
(g) (i) Describe four sources of uncertainty or limitations of the procedure in this experiment.
(ii) Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures.
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532
510
