can you please check my answers and help me with one question?
During a lie dector test, a voltage of 6 V is impressed across two fingers. When a certain question is asked, the resistance between the fingers drops from 400,000 ohms to 200, 000 ohms. What is the current (a) initially through the fingers, and (b) when the resistance between them drops? (this question I don't understand)
How much resistance allows an impressed voltage of 6V to produce a current of 0.006 A ? I got 1000 ohm
What is the resistance of a clothes iron that draws a current of 12 A at 120 V? I got 10 ohm
The current in an incandescent lamp is 0.5A when connected to a 120-V circuit, and 0.2A when connected to a 10-V source. Does the resistance of the lamp change in these cases? Explain your answers and defend it with numerical values?( I got: 120 V/0.5A=240 ohms and 10V/0.2A=50 ohms. Yes the resistance changes in both cases.)
The current in the first problem is V/R in both cases. Just compute the numbers at bot values of R.
Your second answer is correct.
Your third answer is correct.
Yes, the resistance of the tungsten lamp filament increases quite a bit when it gets hotter (as it does with higher voltage operation).
Sure, I'd be happy to help you with your questions!
For the first question about the lie detector test, let's break it down into two parts:
(a) Initially, the resistance between the fingers is 400,000 ohms. To find the current initially through the fingers, we can use Ohm's Law, which states that the current (I) is equal to the voltage (V) divided by the resistance (R).
So, I = V / R = 6 V / 400,000 ohms = 0.000015 A, or 15 μA (microamps).
(b) When the resistance between the fingers drops to 200,000 ohms, we can follow the same process to find the current through the fingers:
I = V / R = 6 V / 200,000 ohms = 0.00003 A, or 30 μA (microamps).
Now, let's move on to the second question:
The question asks how much resistance allows an impressed voltage of 6V to produce a current of 0.006 A.
To find the resistance, we can rearrange Ohm's Law:
R = V / I = 6 V / 0.006 A = 1000 ohms.
So, you are correct! The resistance required to produce a current of 0.006 A with a voltage of 6V is 1000 ohms.
Moving on to the third question about the resistance of a clothes iron:
The question states that the iron draws a current of 12 A at 120 V. To find the resistance, we can again use Ohm's Law:
R = V / I = 120 V / 12 A = 10 ohms.
So, your answer of 10 ohms is correct!
Lastly, let's tackle the question about the resistance of an incandescent lamp:
The lamp has a current of 0.5 A when connected to a 120 V circuit, and a current of 0.2 A when connected to a 10 V source. We'll calculate the resistance in both cases:
For the first case, R = V / I = 120 V / 0.5 A = 240 ohms.
For the second case, R = V / I = 10 V / 0.2 A = 50 ohms.
As you correctly stated, the resistance does change in both cases since the current and voltage values are different.
I hope this helps clarify your answers! Let me know if there's anything else I can assist you with.