Problem 4: In order to calculate the heat loss through the wall of a building, it is necessary to know the temperature difference between the inside and outside walls. If temperatures of 5°C and 20°C are measured on each side of the wall by mercury- in-glass thermometers with a range of 0°C to C50°C and a quoted inaccuracy figure of t1% of full-scale reading, calculate the likely maximum possible error in the calculated figure for the temperature difference.

Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List)
10th Edition
ISBN:9781337399128
Author:Russell E. Smith
Publisher:Russell E. Smith
Chapter13: Heating Control Devices
Section: Chapter Questions
Problem 28RQ
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Problem 4:
In order to calculate the heat loss through the wall of a building, it is necessary to know
the temperature difference between the inside and outside walls. If temperatures of
5°C and 20°C are measured on each side of the wall by mercury- in-glass
thermometers with a range of 0°C to C50°C and a quoted inaccuracy figure of ±1% of
full-scale reading, calculate the likely maximum possible error in the calculated
figure for the temperature difference.
Problem 5:
The power dissipated in a car headlight is calculated by measuring the d.c. voltage
drop across it and the current flowing through it. If the possible errors in the
measured voltage and current values are ±1% and ±2% respectively, calculate the
likely maximum possible error in the power value deduced.
Problem 6:
The resistance of a carbon resistor is measured by applying a d.c. voltage across it
and measuring the current flowing. If the voltage and current values are measured
as 10± 0.1V and 214 ± 5mA respectively, express the value of the carbon resistor.
Problem 7:
The density (d) of a liquid is calculated by measuring its depth (c) in a calibrated
rectangular tank and then emptying it into a mass measuring system. The length
and width of the tank are (a) and (b) respectively and thus the density is given by:
d = m/abc where m is the measured mass of the liquid emptied out. If the
possible errors in the measurements of a, b, c and m are 1%, 1%, 2% and 0.5%
respectively, determine the likely maximum possible error in the calculated
value of the density (d).
Problem 8:
A rectangular-sided block has edges of lengths a, b and c, and its mass is m. If
the values and possible errors in quantities a, b, c and m are as shown below,
calculate the value of density and the maximum likely error in this value using
Kline-McClintock method.
a = 100mm + 1%, b = 200mm ± 1%, c = 300mm ± 1% and m = 20 kg ± 0.5%.
Transcribed Image Text:Problem 4: In order to calculate the heat loss through the wall of a building, it is necessary to know the temperature difference between the inside and outside walls. If temperatures of 5°C and 20°C are measured on each side of the wall by mercury- in-glass thermometers with a range of 0°C to C50°C and a quoted inaccuracy figure of ±1% of full-scale reading, calculate the likely maximum possible error in the calculated figure for the temperature difference. Problem 5: The power dissipated in a car headlight is calculated by measuring the d.c. voltage drop across it and the current flowing through it. If the possible errors in the measured voltage and current values are ±1% and ±2% respectively, calculate the likely maximum possible error in the power value deduced. Problem 6: The resistance of a carbon resistor is measured by applying a d.c. voltage across it and measuring the current flowing. If the voltage and current values are measured as 10± 0.1V and 214 ± 5mA respectively, express the value of the carbon resistor. Problem 7: The density (d) of a liquid is calculated by measuring its depth (c) in a calibrated rectangular tank and then emptying it into a mass measuring system. The length and width of the tank are (a) and (b) respectively and thus the density is given by: d = m/abc where m is the measured mass of the liquid emptied out. If the possible errors in the measurements of a, b, c and m are 1%, 1%, 2% and 0.5% respectively, determine the likely maximum possible error in the calculated value of the density (d). Problem 8: A rectangular-sided block has edges of lengths a, b and c, and its mass is m. If the values and possible errors in quantities a, b, c and m are as shown below, calculate the value of density and the maximum likely error in this value using Kline-McClintock method. a = 100mm + 1%, b = 200mm ± 1%, c = 300mm ± 1% and m = 20 kg ± 0.5%.
Problem 1:
Voltage across a resistance R5 in the circuit of Figure 1 is to be measured by a
voltmeter connected across it.
(a) If the voltmeter has an internal resistance (Rm) of 4750
what is the
measurement error?
(b) What value would the voltmeter internal resistance need to be in order to
reduce the measurement error to 1%?
200 N
250 2
R,
Rm
500 2
R2 500 2
300 N
R2
Figure 1
Problem 2:
The following ten measurements are made of the output voltage from a high gain
amplifier that is contaminated due to noise fluctuations:
1.53, 1.57, 1.54, 1.54, 1.50, 1.51, 1.55, 1.54, 1.56, 1.53
Determine the mean value and standard deviation.
Problem 3:
A 3 volt d.c. power source required for a circuit is obtained by connecting together
two 1.5V batteries in series. If the error in the voltage output of each battery is
specified as ±1%, calculate the likely maximum possible error in the 3 volt power
source that they make up.
Transcribed Image Text:Problem 1: Voltage across a resistance R5 in the circuit of Figure 1 is to be measured by a voltmeter connected across it. (a) If the voltmeter has an internal resistance (Rm) of 4750 what is the measurement error? (b) What value would the voltmeter internal resistance need to be in order to reduce the measurement error to 1%? 200 N 250 2 R, Rm 500 2 R2 500 2 300 N R2 Figure 1 Problem 2: The following ten measurements are made of the output voltage from a high gain amplifier that is contaminated due to noise fluctuations: 1.53, 1.57, 1.54, 1.54, 1.50, 1.51, 1.55, 1.54, 1.56, 1.53 Determine the mean value and standard deviation. Problem 3: A 3 volt d.c. power source required for a circuit is obtained by connecting together two 1.5V batteries in series. If the error in the voltage output of each battery is specified as ±1%, calculate the likely maximum possible error in the 3 volt power source that they make up.
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