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Physics
UTME / JAMB 1993
Thermal Physics
Solution
200g of water at 90^\circC is mixed with 100g of water at 30^\circC. What is the final temperature?
A
50oC
B
60oC
C
70oC
D
80oC
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Heat lost = heat gained
200 x c x (90 - \(\theta\))= 100\(\times\) c \(\times\) (\(\theta - 30\))
Dividing through by 100c, we have
2(\(90 - \theta\)) = (\(\theta - 30\))
simplifying, we have
\(\theta\) = 70^\circ
Source: Myschool Past Questions Archive (Record #27988)
Physics
WAEC / WASSCE 1992
Thermal Physics
Solution
Steel bars, each of length 3.0 m at 28°C, are to be used for constructing a rail line. If the linear expansivity of steel is 1.0 x 10-5°C, what is the safety gap that must be left between successive bars if the highest temperature expected is 40oC?
A
1.2 x 10-1cm
B
8.4 x 10-2cm
C
7.2 x10-2cm
D
3.6 x 10-2cm
E
1.8 x 10-2cm
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Gap ΔL = αL1Δθ = 1.0 x 10-5 x 3 x (40 - 28)
= 3.6 x 10-2
Source: Myschool Past Questions Archive (Record #24254)
Physics
WAEC / WASSCE 1992
Thermal Physics
Solution
A gas which obeys Charles’ law exactly has a volume of 283cm3 at 10oC. What is its volume at 30oC?
A
142cm3
B
293cm3
C
303cm3
D
566cm3
E
849cm3
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Using Charles law:
V1/T1 = V2/T2;
(283 * 303) / 283
V2= 303
Source: Myschool Past Questions Archive (Record #24258)
Physics
WAEC / WASSCE 1992
Thermal Physics
Solution
A metal of mass 1.5 kg was heated from 27oC to 47oC in 4 minutes by a boiling ring of 75 W rating. Calculate the specific heat capacity of the metal, (Neglect heat losses to the surrounding)
A
2.5 X103J kg-10C-1
B
6.0 X102J kg-10C-1
C
2.5 x 102J kg-10C-1
D
1.4 X102J kg-10C-1
E
1.0 x 102J kg-10C-1
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
I.Vt = mcθ; C = I.Vt/mθ = 75 x 4 x 60/1.5 x 20
= 6.0 X102J kg-10C-1
Source: Myschool Past Questions Archive (Record #24262)
Physics
WAEC / WASSCE 1992
Thermal Physics
Which of the following radiations have the highest frequency?
A
Radio waves
B
Light waves
C
X-rays
D
infra-red rays
E
Ultraviolet rays
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #24276)
Physics
WAEC / WASSCE 1992
Thermal Physics
A sheet of paper is placed in the path of a beam of radiations from a radioactive source. Which of the following radiations will pass through the paper?I. Alpha rays II. Beta rays III. Gamma rays
A
I only
B
II only
C
III only
D
II and III only
E
I, II and III
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #24299)
Physics
WAEC / WASSCE 1992
Thermal Physics
The process by which a metal, heated to high temperature, gives off electrons from its surface is known as
A
photoelectric emission
B
thermionic emission
C
radioactive emission
D
Held emission
E
secondary emission
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #24300)
Physics
UTME / JAMB 1992
Thermal Physics
Solution
A bridge made of steel is 600m long. What is the daily variation in its length if the night-time and daytime temperatures are 10^\circC and 35^\circC respectively. The linear expansivity of steel is 0.000012C\(^{-1}\).
A
0.18cm
B
1.80cm
C
18.00cm
D
1800cm
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
\(\alpha\) = \(\frac{extension}{L\Delta\theta}\)
0.000012 = \(\frac{e}{600 \times (35 - 10}\)
= 0.18m
= (0.18 x 100) cm
= 18.0 cm
Source: Myschool Past Questions Archive (Record #28060)
Physics
UTME / JAMB 1992
Thermal Physics
Solution
How much heat is absorbed when a block of copper of mass 0.05kg and specific heat capacity 390Jkg-1K-1 is heated from 20oC to 70oC?
A
39 . 98 x 10-1J
B
9.75 x 102J
C
3.98 x 103J
D
9.75 x 103J
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Q = mc\(\theta\)
= 0.05 x 390 x (70 - 20)
= 975J
Source: Myschool Past Questions Archive (Record #28066)
Physics
UTME / JAMB 1992
Thermal Physics
Solution
Which of the following factors has no effect on the e.m.f. of a primary cell?
A
temperature
B
size of the cell
C
nature of the plate
D
nature of the electrolyte
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
The e.m.f. is primarily influenced by temperature, the nature of the plates, and the nature of the electrolyte, but not by the size of the cell itself.
Source: Myschool Past Questions Archive (Record #28104)
Physics
UTME / JAMB 1992
Thermal Physics
Solution
A platinum resistance thermometer wire has a resistance of 5 ohms at 0oC and 5.5 ohms at 100oC. Calculate the temperature of the wire when the resistance is 5.2 ohms
A
80oC
B
60oC
C
40oC
D
10oC
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
100oC .... 5.5
\(\theta\)oC .... 5.3
0oC .... 5.0
\(\frac{\theta - 0}{100 - 0}\) = \(\frac{5.5 - 5 .0}{5.5 - 5.0}\)
\(\theta\) = 40oC
Source: Myschool Past Questions Archive (Record #28056)
Physics
UTME / JAMB 1991
Thermal Physics
Solution
A thermometer with an arbitrary scale S, of equal division registers -30oS at the ice point and +90oS at the steam point. Calculate the Celsius temperature corresponding to 60oS
A
25.0oC
B
50.0oC
C
66.7oC
D
75.0oC
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
100oC ... 90oS
\(\theta\)oC ... 60oS
0oC ... 30oS
\(\frac{\theta - 0}{100 - 0}\) = \(\frac{60 - (-30)}{90 - (-30)}\)
\(\theta\) = 75oC
Source: Myschool Past Questions Archive (Record #28164)
Physics
UTME / JAMB 1991
Thermal Physics
Solution
A brass rod is 2m long at a certain temperature. What is the length for a temperature rise of 100K, if the expansivity of brass is 18 x 10-6K-1?
A
2.0036m
B
2.0018cm
C
2.1800
D
2.0360m
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(\alpha\) = \(\frac{L_2 - L_1}{L_1 \times \Delta \theta}\)
18 x 10-6 = \(\frac{L_2 - 2}{2\times 100}\)
L = 2.0036m
Source: Myschool Past Questions Archive (Record #28173)
Physics
UTME / JAMB 1991
Thermal Physics
Solution
What is the difference in the amount of heat given out by 4kg of steam and 4kg of water when both are cooled from 100ºC to 80ºC? [the specific latent heat of steam is 2,260,000Jkg\(^{-1}\), specific heat capacity of water is 4200Jkg\(^{-1}\)K\(^{-1}\)]
A
4200J
B
2,260,OOOJ
C
9,040,000J
D
9,380,000J
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
To find the difference in the amount of heat given out by 4 kg of steam and 4 kg of water when both are cooled from 100^\circC to 80^\circC, we need to calculate the heat released by each.
Heat Given Out by Water
The heat given out by water as it cools can be calculated using the formula:
\(Q = mc\Delta T\)
Where:
- m = 4 kg (mass of water)
- c = 4200 (specific heat capacity of water)
- \( \Delta\) T = 100 - 80 = 20K (change in temperature)
Calculating the heat given out by water:
\(Q_{\text{water}} = 4 \times 4200 \times 20 = 336,000 \, \text{J}\)
Heat Given Out by Steam
For steam, we need to consider both the cooling of the steam to water and the cooling of the water from 100^\circC to 80^\circC. The total heat given out by the steam is the sum of the heat released during condensation and the heat released during cooling.
Heat released during condensation: \(Q_{\text{condensation}} = mL\)
Where:
- \( L = 2,260,000 \, \text{J/kg} \) (specific latent heat of steam)
Calculating the heat released during condensation:
\(Q_{\text{condensation}} = 4 \, \text{kg} \times 2,260,000 \, \text{J/kg} = 9,040,000 \, \text{J}\)
Heat released by water as it cools from 100^\circC to 80^\circC:
This is the same calculation we did for water above:
\(Q_{\text{cooling}} = 4 \times 4200 \times 20 = 336,000 \, \text{J}\)
Total heat given out by steam:
\(Q_{\text{steam}} = Q_{\text{condensation}} + Q_{\text{cooling}} = 9,040,000 \, \text{J} + 336,000 \, \text{J} = 9,376,000 \, \text{J}\)
Difference in Heat Given Out
Now, we find the difference in heat given out by steam and water:
\(\text{Difference} = Q_{\text{steam}} - Q_{\text{water}} = 9,376,000 \, \text{J} - 336,000 \, \text{J} = 9,040,000 \, \text{J}\)
The difference in the amount of heat given out by 4 kg of steam and 4 kg of water when both are cooled from 100^\circC to 80^\circC is 9,040,000 J.
Source: Myschool Past Questions Archive (Record #28179)
Physics
UTME / JAMB 1991
Thermal Physics
The absolute temperature of a perfect gas is proportional to the average
A
potential energy of the molecules
B
seperation between the molecules
C
kinetic energy of the molecules
D
velocity of the molecules
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #28182)