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In this experiment, you will measure the currents at two different points in the same circuit and investigate how the currents depend on the total resistance of the circuit.
(a) (i) Set up the circuit as shown in Fig. 1.1.
There are crocodile clips at L, M and N.
Place the crocodile clip at N so that the length $x$ from N to M is approximately 60 cm.
(ii) Measure and record the value of $x$.
(iii) Close the switch.
(iv) Record the current $I_1$ given by ammeter 1. [1]
(v) Record the current $I_2$ given by ammeter 2. [2]
(vi) Open the switch.
(b) Change $x$ and repeat (a) until you have six sets of readings of $x$, $I_1$ and $I_2$ where $x$ is in the range $0.200 , m \leq x \leq 0.800 , m$.
Include values of $\frac{I_2}{I_1}$ and $\frac{1}{x}$ in your table.
(c) (i) Plot a graph of $\frac{I_2}{I_1}$ on the $y$-axis against $\frac{1}{x}$ on the $x$-axis.
(ii) Draw the straight line of best fit.
(iii) Determine the gradient and $y$-intercept of this line.
(d) The quantities $I_1$, $I_2$ and $x$ are related by the equation
$$ \frac{I_2}{I_1} = \frac{P}{x} + Q $$
where $P$ and $Q$ are constants.
Using your answers from (c)(iii), determine the values of $P$ and $Q$.
Give appropriate units. [2]
518
581
587
In this experiment, you will investigate how the motion of a spring depends on its length.
(a) (i) Measure and record the diameter $D$ of the coiled part of the spring as shown in Fig. 2.1. [1]
(ii) Estimate the percentage uncertainty in your value of $D$. [1]
(b) (i) Place the metal strip through the spring as shown in Fig. 2.2.
The length $x$ of the coiled part of the spring below the metal strip should be approximately 1.5 cm.
(ii) Measure and record $x$. [1]
(iii) Calculate the volume $V$ inside the coiled part of the spring below the metal strip using [1]
$$ V = \frac{\pi D^2 x}{4} $$
(c) (i) Clamp the metal strip so that it is horizontal with loop A of the spring at the top. Gently hang a mass of 300 g from loop B, as shown in Fig. 2.3. Ensure that the base of the mass hangs approximately 20 cm above the bench.
(ii) Slowly and gently pull the mass towards the bench by approximately 1 cm.
(iii) Release the mass and watch its movement. The mass will move up and then down, completing a cycle, as shown in Fig. 2.4.
(iv) Measure and record the time for at least 10 cycles. Record enough readings to determine an accurate value for the time $T$ taken for one complete cycle. [2]
(d) (i) Remove the mass from the spring.
(ii) Remove the spring from the metal strip.
(iii) Repeat (b)(i) making $x$ approximately 1.0 cm.
(iv) Measure and record $x$. [1]
(e) Repeat (b)(iii) and (c). [4]
(f) It is suggested that the relationship between $T$ and $V$ is
$$ T^2 = kV $$
where $k$ is a constant.
(i) Using your data, calculate two values of $k$. [1]
(ii) Justify the number of significant figures that you have given for your values of $k$. [1]
(iii) Explain whether your results in (f)(i) support the suggested relationship. [1]
(g) (i) Describe four sources of uncertainty or limitations of the procedure for this experiment. [4]
(ii) Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. [4]
515
543
580
