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In this experiment, you will investigate the relationship between the power dissipated in a filament lamp and the resistance of the lamp.
(a) Assemble the circuit of Fig. 1.1.
(b) Set the power supply voltage to $12V$ and close the switch so that the lamp lights. Record the voltmeter reading $V$ and the ammeter reading $I$.
(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 values of $P$, $R$ and $R^4$, where $P$ is the power dissipated in the lamp and $R$ is the resistance of the lamp.
$(P = VI \text{ and } R = \frac{V}{I})$
(d) (i) Plot a graph of $P$ on the $y$-axis against $R^4$ 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 $P$ and $R$ is
$P = aR^4 + b$
where $a$ and $b$ are constants.
Using your answers from (d)(iii), determine the values of $a$ and $b$. Give appropriate units.
504
518
591
In this experiment, you will investigate how the movement of a tube is affected by fluid friction.
The apparatus has been set up for you as shown in Fig. 2.1. The mass hanger will move up and down if it is pulled down and released.
(a) (i) By adjusting the position of the clamp, lower the spring and mass hanger so that the bottom of the tube is immersed centrally in the oil to a depth $d$ of about 5 cm, as shown in Fig. 2.2.
(ii) Measure and record $d$.
(b) Adjust the distance indicator so that its arrow is level with the bottom of the mass hanger, as shown in Fig. 2.2.
(c) (i) Pull down the mass hanger about 3 cm and release it so that it moves up and down.
Each time the mass hanger moves down, you will see that the lowest position that it reaches changes gradually from 3 cm to 0 cm below the arrow.
(ii) Repeat (i) and start the stopwatch when the mass hanger’s lowest position is 2.0 cm below the arrow. Stop the stopwatch when the lowest position has become 0.5 cm below the arrow.
Record this time $t$.
(d) Estimate the percentage uncertainty in $t$.
(e) (i) By again adjusting the position of the clamp, lower the spring and mass hanger so that $d$ is about 10 cm.
(ii) Repeat (a)(ii), (b) and (c).
(f) (i) It is suggested that the relationship between $t$ and $d$ is $$ t^4 = \frac{k}{d^3} $$ where $k$ is a constant. Using your data, calculate two values of $k$.
(ii) Explain whether your results support the relationship in (i).
(iii) Justify the number of significant figures that you have used for your values of $k$.
(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.
528
569
504
