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Physics
WAEC / WASSCE 2020
Electricity and Magnetism
In photoelectric effect, the number of electrode emitted per second from a metallic surface is proportional to the
A
intensity of the incident radiation
B
frequency of the incident radiation
C
energy of the incident radiation
D
work function of the metal.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #59485)
Physics
WAEC / WASSCE 2020
Electricity and Magnetism
Solution
When two cells of negligible internal resistances and equal e.m.f. denoted by E\(_1\) and E\(_2\) are connected in parallel, combined e.m.f. E is given by
A
E = E\(_1\) + E\(_2\)
B
\(\frac{1}{E} = \frac{1}{E_1} + \frac{1}{E_2}\)
C
E = E\(_1\) = E\(_2\)
D
E = \(\frac{E_1}{E_2}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
If two cells of equal emf s are connected in parallel then the effective emf is equal to the emf of any one of the cells.
Source: Myschool Past Questions Archive (Record #59486)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
In a slide wire bridge, the balance is obtained at a point 25cm from one end of wire 1m long. The resistance to be tested is connected to that end and a standard resistance of 3.6\(\Omega\) is connected to the other end of the wire. Determine the value of the unknown resistance
A
3.2\(\Omega\)
B
1.4\(\Omega\)
C
3.21\(\Omega\)
D
1.2\(\Omega\)
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
\(\frac{R}{3.6} = \frac{75}{25} = \frac{1}{3}\)
3R = 3.6
R = 1.2\(\Omega\)
Source: Myschool Past Questions Archive (Record #54989)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
Which of the following equations is the correct definition of the reactance of an indicator L?
A
Reactance = (Amplitude of voltage) \(\div\) (Amplitude of current)
B
Reactance = (Amplitude of voltage) x (Amplitude of current)
C
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)
D
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)\(\frac{1}{2}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Reactance is the value of an indicator or a capacitor in ohms
Source: Myschool Past Questions Archive (Record #54995)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
When the downward current flows in a straight vertical conductor, the direction of its magnetic field at a point due north of the wire is?
A
Upward
B
North
C
South
D
West
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
At a point due N of the wire, the field is due west, at a point due S of the wire, the field is due eest.
Source: Myschool Past Questions Archive (Record #55058)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
A supply of 400V is connected across capacitors of 3\muf and 6\muf in series. Calculate the charge
A
8 x 10\(^{-4}\)C
B
4 x 10\(^{-2}\)C
C
8 x 10\(^{-3}\)C
D
4 x 10\(^{-8}\)C
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
C\(_T\) = \(\frac{C_1 \times C_2}{C_1 + C_2}\)
= \(\frac{3 \times 6}{3 + 6}\)
= \(\frac{18}{9}\) = 2\muf
Q = CV
⇒ 2 \times 10\(^{-6}\) \times 400
⇒ 800 \times 10\(^{-6}\)C = 8 \times 10\(^{-4}\)C
Source: Myschool Past Questions Archive (Record #55090)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
An alternating current can induce voltage because it has
A
ripple value
B
varying magnetic field
C
weaker magnetic field than direct current
D
high peak value
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
As induced voltage is produced by varying magnetic field. The induced voltage is proportional to the rate of change of magnetic flux linking the coil.
Source: Myschool Past Questions Archive (Record #55227)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
Three resistors with resistance 200\Omega, 500\Omega and 1k\Omega are connected in series. A 6v battery is connected to either end of the combination. Calculate the potential difference between the ends of 200\Omega resistance.
A
0.71V
B
0.7V
C
0.82V
D
0.8V
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Req = 200 + 500 + 1000 = 1700\Omega
P.d
(across
200\Omega)
=
200
1700
\times
6
=
0.71V
Source: Myschool Past Questions Archive (Record #55567)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Solution
The Earth's magnetic equator passes through Jos in Nigeria. At Jos, the
A
angle of variation is zero
B
magnetic declination is 90
C
angle of dip is zero
D
horizontal component at the Earth's field is zero
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
- angle of dip is zero at the magnetic equator
- angle of variation is the same as angle of declination.
Source: Myschool Past Questions Archive (Record #55607)
Physics
UTME / JAMB 2019
Electricity and Magnetism
Diagram
Solution
Which of the following statement about the electromagnet shown above is correct?
Attached Figure / Diagram
A
when the current flows from A to B, the end A will be in north pole
B
when the current flows from A to B, the end A will be south pole
C
when the current flows from A to B, the end B will be south pole
D
none of the above
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
A - B = S - N.
Also, starting end of the current is south while terminating end is North.
Source: Myschool Past Questions Archive (Record #55594)
Physics
WAEC / WASSCE 2019
Electricity and Magnetism
Solution
List three magnetic elements that determine the earth’s magnetic field at a point.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
Magnetic elements that determine the earth’s magnetic field at a point
- Angle of dip/inclination
- angle of declination/variation
- horizontal component of the earth’s magnetic field
Source: Myschool Past Questions Archive (Record #56502)
Physics
WAEC / WASSCE 2019
Electricity and Magnetism
Solution
Explain each of the following terms as used in Electronics.
(a) free electrons;
(b) holes.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
Explanation of terms
(a) Free electrons; Negative charge carriers
(b) Holes; Positive charge carriers
Source: Myschool Past Questions Archive (Record #56510)
Physics
WAEC / WASSCE 2019
Electricity and Magnetism
The induced current in a coil always flows in a direction so as to oppose the change that causes it. This statement is known as
A
Coulomb's law
B
Lenz's law
C
Faraday's law
D
Ampere's law
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 #58785)
Physics
WAEC / WASSCE 2019
Electricity and Magnetism
Which of the following instruments can be used to compare the magnitudes of charges on two given bodies?
A
Electrophorus
B
Ebonite rod
C
Gold-leaf electroscope
D
Proof planes
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 #58787)
Physics
WAEC / WASSCE 2019
Electricity and Magnetism
Diagram
Solution
Which of the following graphs above of a charge Q against potential difference V across the capacitor is correct?
Attached Figure / Diagram
A
A
B
B
C
C
D
D
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
C = \(\frac{\text{Q}}{\text{V}}\) ⇒ Q = CV which means that Q Is directly proportional to V.
Source: Myschool Past Questions Archive (Record #58847)