10: Exam Questions

Question 1

Which statement about a capacitor in a series circuit is true?
Others are all numerical

Answer 1

The charges on the plates are equal and opposite

Question 2

What does λ mean in the decay equation?

Answer 2

probability that a nucleus decays/fraction of nuclei which
decay;
in unit time/1s;

Question 3

Find the capacitance of a capacitor using a current/time graph. Also given V. Use the time constant

Answer 3

Time constant: τ = RC

*time for current to drop by 1/e. *half life/ln2

Question 4

The activity of a radioactive material is measured. Describe how the correction for background radiation is made

Answer 4

repeat the procedure without the protactinium; subtract result from recorded value with protactinium;

Question 5

Calculate the capacitance. Given the voltage, and an I/t graph

Answer 5

EITHER use of half-life = 0.69RC = 33±1 s / 53±1 s; OR use of RC = 1/e drop time = 49±1 s / 69±1 s; OR data from graph, use of current equation (I=Ie^-t/RC)