Question 1

Paper 2Medium4 marks

During a Millikan-type investigation, the charge magnitudes of positively charged oil droplets are measured. Droplets A and B coalesce to form droplet C. No charge is transferred to or from the surroundings during coalescence. Figure 1 also shows measurements for droplets D and E. Each plotted measurement has an uncertainty of ±0.1 in the units shown.

ABCDE0123456789DropletMeasured charge magnitude, q / (10⁻¹⁹ C)3.24.78.01.66.3
(a)

Use Figure 1 to estimate the elementary charge and explain how the measurements provide evidence that electric charge is quantized.

[2]
(b)

Using your estimate in (a), assess whether the coalescence of A and B is consistent with conservation of electric charge.

[2]

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