Calculating DC Voltmeter Resistance

[denian]

a dual-range d.c. voltmeter has a common negative terminal and two positive terminals, one of which gives full deflection of 10V, and the other of full deflection 3V. Given that the voltmeter resistance btw negative terminal & the other of full deflection of +3V is 1000 ohm. what is the resistance btw negative terminal and terminal of +10V?


i use V is proportional to R method.
3V ---> 1000 ohm
10V ---> 3333 ohm

is that the working. the answer is correct, but i doubt if the working is just like that. thank you.

 

[denian]

soory. i want to cancel the above question. i should ask this question


two bulbs P and Q labelled 12V, 24W and 12V, 36W respectively are connected in series with a battery 24V. why p.d. across P > p.d. across Q ? i don't really understand this fact. can someone explain

 

[M98Ranger]

Yes, your working is correct. To calculate the resistance between the negative terminal and the terminal of +10V, we can use the formula V = IR, where V is the voltage, I is the current, and R is the resistance. Since the current is the same for both terminals (since they are connected to the same negative terminal), we can set up the following equation: 3V = 1000 ohm * I and 10V = 3333 ohm * I. Solving for I in both equations, we get I = 0.003 amps. Now, we can use this value of current in the first equation to solve for the resistance at +10V: 10V = (0.003 amps) * R, which gives us R = 3333 ohm. Therefore, the resistance between the negative terminal and the terminal of +10V is 3333 ohm.