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Physics
WAEC / WASSCE 2013
Current Electricity & Electric Circuits
Solution
You are provided with a constantan wire, a2 \(\Omega\)standard resistor, an accumulator E, an ammeter A, a key K, and other necessary apparatus.
Measure and record the emf of the accumulator provided
Connect a circuit as shown in the diagram above.
Close the key, read and record the ammeter reading \(l_o\) when the crocodile clip is not in contact with the Constantan wire.
Open the key with the clip making contact with the wire, when d=90cm, close the key. Read and record the ammeter reading l.
Evaluate d\(^{_1}\)
Repeat the procedure for four other values of d=80, 70, 60, and 50 cm
In each case, read and record the ammeter reading and evaluatre d\(^{_1}\).
Tabulate your readings.
Plot a graph with I on the vertical axis and d\(^{_1}\) on the horizontal aXIS.
Determine the slope, S of the graph and its intercept, c, on the vertical axis.
Evaluate k = \(\frac{c}{s}\)
Using your graph, determine the current I when d=55cm.
State two precautions taken to obtain accurate results.
(b)i. Explain what is meant by the potential difference between two points in an electric circuit.
ii. State two factors on which the resistance of a wire depends.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
d/cm
I/A
d\(^{-1}\)/cm\(^{-1}\)
80.0
0.23
0.0125
70.0
0.25
0.0143
60.0
0.31
0.0167
50.0
0.34
0.0200
40.0
40.0
0.0250
Slope, SI = \(\frac{\bigtriangleup {I}}{\bigtriangleup {d}^{-1}}\) = \(\frac{0.40-0.13}{0.024-0.006}\)
= \(\frac{(0.27)A}{(0.018)cm^{-1}}\)
= 15A/cm\(^{-1}\)
Intercept C on the vertical axis = 0.04A
k = c/s = \(\frac{0.04}{15}\) = 0.00267 = 2.67 x 10\(^{-3}\)
From the graph, when d = 55cm, I = 0.31A
Precautions; I
- ensured that the keys was open after each reading so that the battery did not run down quickly.
- ensured there was zero error when taking the ammeter reading.
- Key was removed when readings were not being taken
- ensured terminals are clean/tight
- Noted and corrected/avoided zero error on ammeter metre rule
(b)i. The potential difference between two points in an electric circuit is the work done (in joules) when one coulomb of electric charge moves from one point to the other
ii. - Nature of wire/resistivity
- Length of wire
- Cross-sectional area of wire/thickness of wire
- Temperature
Source: Myschool Past Questions Archive (Record #59996)
Chemistry
UTME / JAMB 2013
Nature of Matter & Separation Techniques
Solution
The presence of an impurity in substance will cause the melting point to
A
be zero
B
reduce
C
increase
D
be stable
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Impurities disrupt the repeating pattern of forces that holds the solid together. So a smaller amount of energy is required to melt the part of the solid surrounding the impurity. If less energy is required, then this explains the melting point depression (lowering) observed from impure solids. The more impure the solid is, the more the structure is disrupted and the greater the variation in intermolecular forces in different areas of the solid.
Source: Myschool Past Questions Archive (Record #27428)
Chemistry
UTME / JAMB 2013
Stoichiometry, Mole Concept & Volumetric Analysis
What volume of carbon (ll) oxide is produced by reacting excess carbon with 10 dm3 of oxygen?
A
5 dm 3
B
20 dm 3
C
15 dm 3
D
10 dm 3
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #27429)
Chemistry
UTME / JAMB 2013
Stoichiometry, Mole Concept & Volumetric Analysis
The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is
A
carbon-14
B
phosphorus-32
C
cobalt-60
D
iodine-131
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #27431)
Chemistry
UTME / JAMB 2013
Chemical Bonding & Intermolecular Forces
The shape of the carbon (lV) oxide molecule is
A
pyramidal
B
linear
C
angular
D
tetrahedral
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #27432)
Chemistry
UTME / JAMB 2013
Chemical Bonding & Intermolecular Forces
Solution
Which of the following molecules is held together by hydrogen bond?
A
CH4
B
HBr
C
H2SO4
D
HF
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
HF is held by hydrogen bonding.
Source: Myschool Past Questions Archive (Record #27433)
Chemistry
UTME / JAMB 2013
Atomic Structure, Orbitals & Nuclear Chemistry
The bond formed between two elements with electron configurations 1s2 2s2 2p6 3s2 and 1s2 2s2 2p4 is
A
metallic
B
covalent
C
dative
D
ionic
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #27434)
Chemistry
UTME / JAMB 2013
Periodic Table & Periodicity
The constituent of air that acts as a diluent is
A
nitrogen
B
carbon (IV) oxide
C
noble gases
D
oxygen
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #27435)
Chemistry
UTME / JAMB 2013
Stoichiometry, Mole Concept & Volumetric Analysis
Steam changes the colour of anhydrous cobalt (ll) chloride from
A
white to red
B
blue to white
C
blue to pink
D
white to blue
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #27436)
Chemistry
UTME / JAMB 2013
Water, Solutions & Solubility
An example of a hygroscopic substance is
A
CuO (S).
B
MgCL2(S).
C
CaCL2(S).
D
NaOH(S).
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #27437)
Chemistry
UTME / JAMB 2013
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
The solvent used for removing grease stain is
A
turpentine
B
ammonia solution
C
ethanol
D
solution of borax in water
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Ammonia solution (also known as aqueous ammonia or ammonium hydroxide) is frequently used in laundries and household cleaners as a solvent for removing grease and oil stains. It is effective because it reacts with fatty acids in grease to form soluble soaps (a process called saponification) or helps emulsify the oils so they can be washed away with water.
Source: Myschool Past Questions Archive (Record #27439)
Chemistry
UTME / JAMB 2013
Air & Environmental Chemistry
In a water body, too much sewage leads to
A
a decrease in the temperature of the water which cause in death of aquatic animals
B
an increase in the number of aquatic animals in the water
C
an increase in the bacterial population which reduces the level of oxygen in the water
D
a decrease in the bacterial population which increases the level of oxygen in the water
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #27440)
Chemistry
UTME / JAMB 2013
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
10.0 dm3 of water was added to 2.0 mol dm-3 of 2.5dm3 solution of HCl. What is the concentration of the final solution in mol dm-3?
A
0.4
B
8.0
C
2.0
D
0.5
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
C1V1 = C2V2
C2 = \(\frac{C_1V_1}{V_2}\)
= \(\frac{2.0 \times 2.5}{12.5}\)
= 0.4mol/dm-3
Source: Myschool Past Questions Archive (Record #27441)
Chemistry
UTME / JAMB 2013
Acids, Bases, pH & Salts
Three drops of a 1.0 mol dm-3 solution of HCl was added to 20 cm3 of a solution of pH6.4. The pH of the resulting solution will be
A
close to that of pure water
B
less than 6.4
C
greater than 6.4
D
unaltered
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #27442)
Chemistry
UTME / JAMB 2013
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following substances is not a salt?
A
Aluminium oxide
B
Sodium hydrogentrioxosulphate (V)
C
Sodium trioxocarbonate (V)
D
Zinc chloride
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #27443)