Solving High Voltage Problems: Circuit Diagrams & Current Calculations

[alonzo]

Please help me wif these problems! I have no idea.
A person with a body resistance between his hands of 10 kohms accidently grasps the terminals of a 20 kV power supply.
(a) Draw a circuit diagram including all the data.
(b) If the internal resistance of the power supply is 2000 ohmns, what is the current through his body?
(c) What is the power dissapated in his body?
(d) If the power supply is to be made safe by increasing its internal resistance, what should the internal resistance be for the maximum current in this situation to be 1.00 mA or less?

Thanks 4 ur help!

 

[maverick280857]

Hi Alonzo

All your questions can be answered if you do part (a) correctly. You haven't included your solution here. First, please do so, so that we know where you're going wrong/facing difficulty.

First off, I'd say you have a power supply (a power source--a seat of emf in this case), a <few> resistance(s) in the circuit.

1. What is the expression for current in a circuit containing a seat of emf V and resistance R?
2. What is the expression for the power?
(Hint: Think about Ohm's Law)
3. What is your specific problem with this?

Cheers
Vivek

 

[M98Ranger]

(a) The circuit diagram would consist of the 20 kV power supply connected in series with the person's body resistance of 10 kohms and the internal resistance of 2000 ohms. The power supply would have a positive terminal connected to the person's hand and a negative terminal connected to the other hand.
(b) To calculate the current through his body, we can use Ohm's Law: I = V/R. Plugging in the values, we get I = (20,000 V)/(10,000 ohms + 2000 ohms) = 1.67 mA.
(c) The power dissipated in his body can be calculated using the formula P = I^2*R, where I is the current and R is the resistance. Plugging in the values, we get P = (0.00167 A)^2 * 10,000 ohms = 0.0278 watts.
(d) To make the power supply safe by reducing the current to 1.00 mA, the internal resistance should be equal to or greater than (20,000 V)/(0.001 A) = 20,000,000 ohms. So, the internal resistance should be at least 20,000,000 ohms to ensure the maximum current through the person's body is 1.00 mA or less.