©LEB/Weekly Evaluation/2nd March 2021
With LEADEX, you just have to believe!
LEADERS OF EXCELLENCE
Leading With
Excellence LEADEX
LEADEX is a chain of enterprises comprising of dynamic and
excellent students and startup entrepreneurs from science
professional schools in Cameroon who have as mission ‘promoting
excellence in academics and developing excellent and creative youths;
developing students in the fields of team work, leadership and
entrepreneurship; ensuring entrance into professional schools; making
students discover and fully utilize their potentials.’
We offer home classes, weekend classes, pre-preparatory classes
and preparatory classes.
Contacts: 671904899/672881839/652316162/670771993/657640444
LEADEX EXAMINATION BOARD (LEB)
MARCH 2021 ADVANCED LEVEL
Subject Title PHYSICS
Subject Code Number 0780
Paper Number 2
Time allowed = 1.5 hours (5:15 pm – 6:45 pm)
INSTRUCTIONS:
➢ Answer ALL questions.
➢ You are reminded of the necessity of good English and orderly presentation of
your answers.
➢ In calculations, you are advised to show all the steps in your working, giving
your answer at each stage.
➢ Calculators are allowed.
1
LEADEX Leading with excellence…!
, ©LEB/Weekly Evaluation/2nd March 2021
With LEADEX, you just have to believe!
Q1.) a.) What do you understand by the following:
i.) a physical quantity
ii.) homogeneity of a physical equation
ii.) dimensional analysis. (3 marks)
𝑑𝑄
b.) The rate of thermal energy transfer perpendicular to the faces of a welled insulated
𝑑𝑡
rectangular slab of thickness 𝑙, cross-sectional area 𝐴 and thermal conductivity 𝑘 is given by
𝑑𝑄 ∆𝜃
= −𝑘𝐴
𝑑𝑡 𝑙
where ∆𝜃 is the temperature difference delimiting the slab.
i.) Explain the significance of the minus sign and of the ratio ∆𝜃/𝑙. (2 marks)
ii.) Determine the dimensions of 𝑘. (3 marks)
iii.) A copper hot-water cylinder of length 1.0 m and radius 0.20 m is lagged by 2.0 cm of
material of thermal conductivity 0.40 SI. Estimate the temperature of the outer surface of
the lagging, assuming heat loss is through the sides only, if heat has to be supplied at a rate
of 0.25 𝑘𝑊 to maintain the water at a steady temperature of 60°𝐶. (3 marks)
Q2.) a.) State the following:
i.) Coulomb’s law of electrostatics ii.) Newton’s law of universal gravitation. (2 marks)
b.) State two differences and two similarities between the gravitational force and the
electrostatic force. (4 marks)
c.) A hydrogen atom consists of a proton and an electron at an average separation of
5.2 × 10−11 𝑚.
i.) Show, by calculation, that the gravitational force between the two is very negligible
compared to the electrostatic force. (3 marks)
ii.) Calculate the electric field strength that each experiences due to the other.
What is the direction of this field? (2 marks)
iii.) Assuming the electron orbits the proton, calculate the duration per revolution. (3 mrks)
Q3.) a.) State the laws of electromagnetic induction. (2 marks)
b.) A 2.5Ω square coil of side 20 cm with 550 turns is kept in a uniform magnetic field of
0.75𝑇. The plane of the coil is inclined at an angle of 30° to the field.
i.) Calculate the magnetic flux through the coil. (2 marks)
ii.) Calculate the induced emf if the coil is suddenly pulled out of the field in 0.6𝑠. (2 marks)
iii.) How many electrons flow through the coil in this time? (2 marks)
iv.) Draw a diagram to show the direction of the induced current. Explain. (2 marks)
Q4.) The diagram shows a pair of parallel plates connected to a 2.5𝑘𝑉 supply. An oil drop of
mass 0.050𝑔 between the plates carries a charge of 10𝑒.
𝐴
𝐷
3.0 mm 6.0 mm 2.5𝑘𝑉
𝐶
𝐵
2
LEADEX Leading with excellence…!
With LEADEX, you just have to believe!
LEADERS OF EXCELLENCE
Leading With
Excellence LEADEX
LEADEX is a chain of enterprises comprising of dynamic and
excellent students and startup entrepreneurs from science
professional schools in Cameroon who have as mission ‘promoting
excellence in academics and developing excellent and creative youths;
developing students in the fields of team work, leadership and
entrepreneurship; ensuring entrance into professional schools; making
students discover and fully utilize their potentials.’
We offer home classes, weekend classes, pre-preparatory classes
and preparatory classes.
Contacts: 671904899/672881839/652316162/670771993/657640444
LEADEX EXAMINATION BOARD (LEB)
MARCH 2021 ADVANCED LEVEL
Subject Title PHYSICS
Subject Code Number 0780
Paper Number 2
Time allowed = 1.5 hours (5:15 pm – 6:45 pm)
INSTRUCTIONS:
➢ Answer ALL questions.
➢ You are reminded of the necessity of good English and orderly presentation of
your answers.
➢ In calculations, you are advised to show all the steps in your working, giving
your answer at each stage.
➢ Calculators are allowed.
1
LEADEX Leading with excellence…!
, ©LEB/Weekly Evaluation/2nd March 2021
With LEADEX, you just have to believe!
Q1.) a.) What do you understand by the following:
i.) a physical quantity
ii.) homogeneity of a physical equation
ii.) dimensional analysis. (3 marks)
𝑑𝑄
b.) The rate of thermal energy transfer perpendicular to the faces of a welled insulated
𝑑𝑡
rectangular slab of thickness 𝑙, cross-sectional area 𝐴 and thermal conductivity 𝑘 is given by
𝑑𝑄 ∆𝜃
= −𝑘𝐴
𝑑𝑡 𝑙
where ∆𝜃 is the temperature difference delimiting the slab.
i.) Explain the significance of the minus sign and of the ratio ∆𝜃/𝑙. (2 marks)
ii.) Determine the dimensions of 𝑘. (3 marks)
iii.) A copper hot-water cylinder of length 1.0 m and radius 0.20 m is lagged by 2.0 cm of
material of thermal conductivity 0.40 SI. Estimate the temperature of the outer surface of
the lagging, assuming heat loss is through the sides only, if heat has to be supplied at a rate
of 0.25 𝑘𝑊 to maintain the water at a steady temperature of 60°𝐶. (3 marks)
Q2.) a.) State the following:
i.) Coulomb’s law of electrostatics ii.) Newton’s law of universal gravitation. (2 marks)
b.) State two differences and two similarities between the gravitational force and the
electrostatic force. (4 marks)
c.) A hydrogen atom consists of a proton and an electron at an average separation of
5.2 × 10−11 𝑚.
i.) Show, by calculation, that the gravitational force between the two is very negligible
compared to the electrostatic force. (3 marks)
ii.) Calculate the electric field strength that each experiences due to the other.
What is the direction of this field? (2 marks)
iii.) Assuming the electron orbits the proton, calculate the duration per revolution. (3 mrks)
Q3.) a.) State the laws of electromagnetic induction. (2 marks)
b.) A 2.5Ω square coil of side 20 cm with 550 turns is kept in a uniform magnetic field of
0.75𝑇. The plane of the coil is inclined at an angle of 30° to the field.
i.) Calculate the magnetic flux through the coil. (2 marks)
ii.) Calculate the induced emf if the coil is suddenly pulled out of the field in 0.6𝑠. (2 marks)
iii.) How many electrons flow through the coil in this time? (2 marks)
iv.) Draw a diagram to show the direction of the induced current. Explain. (2 marks)
Q4.) The diagram shows a pair of parallel plates connected to a 2.5𝑘𝑉 supply. An oil drop of
mass 0.050𝑔 between the plates carries a charge of 10𝑒.
𝐴
𝐷
3.0 mm 6.0 mm 2.5𝑘𝑉
𝐶
𝐵
2
LEADEX Leading with excellence…!
