Aga Khan Higher Secondary School Gilgit, Grade 12 first bimonthly exam. 10-OCT-2023.

 

Grade 12                                                            AKHSS Gilgit                                  Bi monthly exam     

Physics                                                                10-Oct-2023                          Facilitator: Sadiq Saleem

 

Tick the correct option. Over marking is not allowed. Each question from 1-5 carries 1 mark.

 

1.      1. If a solid metallic sphere contains positive charges Q, then according to Gauss’s law, the position of charges Q is uniformly

a.       Concentrated at center of the sphere

b.      Distributed on inner surface of the sphere

c.       Concentrated inside and outside the sphere

d.      Distributed on the outer surface of the sphere

2.     2.  If the distance between two identical charges is doubled, then the force of repulsion between them decreases by

a.       two-third of the previous value.

b.      one-third of the previous value.

c.        one-fourth of the previous value.

d.       three-fourth of the previous value

3.      3. What is the value of R4 in the given Wheatstone bridge?

a.       10 Ω

b.       15 Ω

c.        30 Ω

d.       60 Ω

4.      4. Displacement of positive and negative charges in a conductor by an electric field produce

a.       electric flux.

b.       magnetic flux.

c.        electric dipole.

d.       magnetic intensity.

5.      5. If three capacitors of different capacitances are connected in series, then the quantity that remains the same will be

a.        charge.

b.       voltage.

c.       current.

d.      capacitance.

 

Q6. Show that the time constant has the same units as time?    (3 marks)

Q7. How introducing a medium between plates of a capacitor affects its capacitance?  (2 marks)

Answer:

When a medium is placed between the plates of a capacitor, the capacitance increases. This is because of the effect of polarization. The sides of the medium facing the plates of the capacitor will induce charges opposite to that of the charges on the capacitor plates, this results in the decrease in distance between the opposite plate and nearer the opposite plates stronger will be the electric field                                            ,

Mathematically:                  

                                   C =

Q8.  Differentiate resistance and resistivity.                                                                                 (2 marks)

Answer:

Resistance	Resistivity
The opposition offered by the conductor against the flow of current is called resistance.	Resistance offered by a conductor of cross sectional area 1 and length 1m is called resistivity.

 

Q9. A conductor of resistance 2ohms length 30cm and cross sectional area 3cm x 3 cm carries a current 10A. determine the resistivity.                             (3 marks)

Answer:

 

Q10.

 If R1= 2ohms, R2= 4ohms and R3 = 6ohms, determine the current flowing in the given circuit. How the value of the current will change if a resistance of 10ohms is connected in series with the circuit.                              (5 marks)

Answer: