The voltmeter is set to the more sensitive range and then used in a circuit - AQA - A-Level Physics - Question 3 - 2021 - Paper 3

The mirror is used to help the user read the scale accurately. It aids in reducing parallax error, as it allows the user to align their line of sight with the needle reflecting off the mirror. This ensures the scale can be read directly without any misinterpretations.

To determine the percentage uncertainty in T₁₅:

1. Calculate the mean of the recorded times from Table 1.
2. Find the maximum and minimum times.
3. Use the formula for percentage uncertainty: ext{Percentage Uncertainty} = rac{ ext{Max Value} - ext{Min Value}}{ ext{Mean Value}} imes 100
4. In this case, the recorded values range and the resulting calculation lead to the final percentage uncertainty.

The time constant (τ) of the circuit can be derived from the formula: $au = R imes C$ Where R is the resistance and C is the capacitance. Given the discharge readings and the calculated values, it can be shown that τ approximates to about 17 s.

Before connecting capacitor C, the student should ensure that the potential difference across C does not exceed 3 V. To do this, she can use a lower supply voltage or gradually connect the capacitor while monitoring the voltage. Furthermore, she should reset the voltmeter to 0 V to ensure accurate readings.

To get an accurate result for the time constant, she should perform multiple trials with consistent methods of measurement. She needs to take average readings of discharge times to minimize errors and ensure that the voltmeter is correctly calibrated. Each measurement must be taken from the same initial voltage to maintain uniformity in her results.

1. The values were chosen to avoid exceeding the full-scale range of the voltmeter, ensuring accurate readings without damaging the equipment.
2. The voltmeter values allow for a range of readings that provide sufficient data points for analysis, ensuring that clear trends are shown in the experimental data.

Using the graph from Figure 8, the student can determine the gradient which relates to the resistance. The relationship can be expressed as: R = -rac{1}{ ext{slope}} After calculating using the values derived from the graph, the resistance value settles around 16 kΩ.

To find the current in the voltmeter at t = 10 s, apply the formula: I = rac{V}{R} Substituting the known values from the experiment as necessary will yield the current at that time.