Internal resistance problem.
Suppose that in Figure 3.3, Vo=13V, R1=250kphm, R2=375kohm, and Ri=1.9Mohm. Initially, the voltmeter is disconnected.
EXAMPLES:
What is the voltage across R2? [Answer: 7.8 V.]
What is the voltage across R2 with the meter connected? [Answer: 7.22926829268293 V.]
QUESTION:
If the internal resistance of the meter were 15 M , what is the voltage across R2?
To find the voltage across R2 with the meter connected, you need to consider the effect of the internal resistance of the meter.
Here are the steps to solve the problem:
1. Calculate the total resistance in the circuit:
R_total = R1 + R2 + Ri
In this case, R1 = 250 kohm, R2 = 375 kohm, and Ri = 1.9 Mohm. Plug in these values and calculate:
R_total = 250 kohm + 375 kohm + 1.9 Mohm
2. Calculate the current flowing through the circuit using Ohm's Law:
I = Vo / R_total
In this case, Vo = 13 V (given). Plug in the values and calculate:
I = 13 V / R_total
3. Calculate the voltage across R2 using Ohm's Law:
V_R2 = I * R2
In this case, R2 = 375 kohm. Plug in the values and calculate:
V_R2 = I * 375 kohm
Now, let's consider the effect of the meter's internal resistance.
4. Add the internal resistance of the meter to the total resistance:
R_total_with_meter = R_total + 15 Mohm
5. Recalculate the current flowing through the circuit using Ohm's Law:
I_with_meter = Vo / R_total_with_meter
6. Recalculate the voltage across R2 using Ohm's Law:
V_R2_with_meter = I_with_meter * R2
Plug in the values and calculate to find the voltage across R2 with the meter connected, assuming its internal resistance is 15 Mohm.