The girl in (Figure 1) has her hand on the sphere of a Van de Graaff generator that is at a potential of 400,000 V. She is standing on an insulating platform, so no current flows through her. But what happens if she touches something that is grounded? Is she still safe? (Figure 2) shows the equivalent circuit. CVDG = 20 pF represents the capacitance of the Van de Graaff sphere, CgirlCgirl = 100 pF is the capacitance of the girl's body, and R = 5.0 kΩ is the resistance of her body, from one hand to the other. The switch is closed when she touches ground. Part A: What is the initial current at the instant the switch is closed? Express your answer with the appropriate units. Part B: What is the time constant for the current to decay? Express your answer with the appropriate units. Part C: Occupational safety experts have found that a shock is safe if the product of the voltage, the current, and the time the current is delivered is less than 13.5 V⋅A⋅s = 13.5 J. Estimate this product during one such time constant assuming constant current as an approximation. Express your answer in joules. Part D: Is this shock safe?
The girl in (Figure 1) has her hand on the sphere of a Van de Graaff generator that is at a potential of 400,000 V. She is standing on an insulating platform, so no current flows through her. But what happens if she touches something that is grounded? Is she still safe? (Figure 2) shows the equivalent circuit. CVDG = 20 pF represents the capacitance of the Van de Graaff sphere, CgirlCgirl = 100 pF is the capacitance of the girl's body, and R = 5.0 kΩ is the resistance of her body, from one hand to the other. The switch is closed when she touches ground.
Part A: What is the initial current at the instant the switch is closed? Express your answer with the appropriate units.
Part B: What is the time constant for the current to decay? Express your answer with the appropriate units.
Part C: Occupational safety experts have found that a shock is safe if the product of the voltage, the current, and the time the current is delivered is less than 13.5 V⋅A⋅s = 13.5 J. Estimate this product during one such time constant assuming constant current as an approximation. Express your answer in joules.
Part D: Is this shock safe?
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