( a ) A voltmeter and an ammeter can be connected as shown in Fig. 26–70a to measure a resistance R . If V is the voltmeter reading, and I is the ammeter reading, the value of R will not quite be V / I (as in Ohm’s law) because some of the current actually goes through the voltmeter. Show that the actual value of R is given by 1 R = I V − 1 R V . where R V is the voltmeter resistance. Note that R ≈ V / I if R V ≫ R. ( b ) A voltmeter and an ammeter can also be connected as shown in Fig. 26–70b to measure a resistance R . Show in this case that R = V I − R A , where V and I are the voltmeter and ammeter readings and R A is the resistance of the ammeter. Note that R ≈ V / I if R A ≪ R . FIGURE 26–70 Problem 81.
( a ) A voltmeter and an ammeter can be connected as shown in Fig. 26–70a to measure a resistance R . If V is the voltmeter reading, and I is the ammeter reading, the value of R will not quite be V / I (as in Ohm’s law) because some of the current actually goes through the voltmeter. Show that the actual value of R is given by 1 R = I V − 1 R V . where R V is the voltmeter resistance. Note that R ≈ V / I if R V ≫ R. ( b ) A voltmeter and an ammeter can also be connected as shown in Fig. 26–70b to measure a resistance R . Show in this case that R = V I − R A , where V and I are the voltmeter and ammeter readings and R A is the resistance of the ammeter. Note that R ≈ V / I if R A ≪ R . FIGURE 26–70 Problem 81.
(a) A voltmeter and an ammeter can be connected as shown in Fig. 26–70a to measure a resistance R. If V is the voltmeter reading, and I is the ammeter reading, the value of R will not quite be V/I (as in Ohm’s law) because some of the current actually goes through the voltmeter. Show that the actual value of R is given by
1
R
=
I
V
−
1
R
V
.
where RV is the voltmeter resistance. Note that R ≈ V/I if RV ≫ R. (b) A voltmeter and an ammeter can also be connected as shown in Fig. 26–70b to measure a resistance R. Show in this case that
R
=
V
I
−
R
A
,
where V and I are the voltmeter and ammeter readings and RA is the resistance of the ammeter. Note that R ≈ V/I if RA ≪ R.
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During an experiment to verify Ohm's law, the voltage supplied and the current through a circuit are measured.
[Voltage is measured in Volt (V) and current in Ampere (A)].
ww
R
on
Battery
The measured value of the current is I = 3.1 ± 0.2 A and that of the voltage is V = 14 0.5 V. The resistance of
the circuit (in N) can be calculated using the formula, R = V/I,
Calculate the,
a) Resistance (in 2) =
b) Fractional uncertainty in the resistance =
c) Absolute uncertainty (in 2) in the resistance=
(b) Determine the voltage across resistor 2.5 Q , v (show full calculation)
60 Q
12 Q
+ v -
2.5 Q
80 Q
40 V
15 Q
20 2
(b)
Consider a particular phone that has a battery rated at 4,000 mAh. The battery operates at a potential difference of 3.90 V. How much energy, in units of kilowatt-hours, is stored in a fully charged battery?
kWh
(c)
If electricity costs $0.12 (or 12.0 cents) per kilowatt-hour, what is the value of the total amount of energy stored in this battery? Express your answer in cents (or 0.01 of a dollar).
¢
(d)
When the phone is idle (that is, turned on but not making calls or texts, using GPS, or running any power-hungry apps), it will operate continuously for 29.2 hours from a fully charged battery, until the battery runs out. How much average current does the phone draw while idle? Express your answer in milliamperes.
mA
Chapter 26 Solutions
Physics for Scientists and Engineers with Modern Physics
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.
How To Solve Any Resistors In Series and Parallel Combination Circuit Problems in Physics; Author: The Organic Chemistry Tutor;https://www.youtube.com/watch?v=eFlJy0cPbsY;License: Standard YouTube License, CC-BY