Q3.3 What is the total charge delivered by the lightning bolt?
Correct Answer:
• 3.5 C
Question Score: 4/4
Q3.4 You decide to protect your house by installing an iron lightning rod. You need it
to be 5 m long, and for safety reasons, you do not want the potential difference
between the top and bottom to exceed 100 V during a lightning strike. What
diameter rod should you get? (The resistivity of iron is 9.71 × 10-8 Ω·m)
The wrong answer(s) that you chose:
• 8.8 mm
Correct Answer:
• 1.8 cm
-guess
Question Score: 2/4
$$d^2 = \frac{4PLI}{\pi V} \rightarrow d^2 = \frac{4 \times 9.71 \times 10^{-8} \times 5}{\pi \times 100} \rightarrow 1.8 cm$$
Q3.5 You are out in a rainstorm and happen to be holding on to your newly installed
lightening rod 1.5 m above the ground. (3.5 m from the top, and it is grounded
at the bottom.) Your feet are firmly planted on the ground. Lightening strikes
as you hold on to the rod. What happens to you? (How much current flows
through you?) The resistance of a person in a rainstorm is about 1000 Ω
The wrong answer(s) that you chose:
• Nothing - Electricity follows the path of least resistance, so it all stays in
the lightning rod.
• You can't let go of the rod (10-20 mA)
• You can't breath (50-99 mA)
• Your heart goes into v-fib. (irregular heart spasms) You die unless there
happens to be a defibrillator near by. (100-200 mA)
• Survival would be a miracle (¿0.5 A)
• Can't feel it (less than 1 mA)
• You get a good zap. It hurts (1-9 mA)
Correct Answer:
• It's hard to breath (21-50 mA)
Question Score: 0.03125/4