MCQ on magnetic effect

MAGNETIC EFFECTS OF ELECTRIC CURRENT

Multiple Choice Questions

1. Choose the incorrect statement from the following regarding magnetic lines of field

(a) The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points

(b) Magnetic field lines are closed curves

(c) If magnetic field lines are parallel and equidistant, they represent zero field strength

(d) Relative strength of magnetic field is shown by the degree of closeness of the field lines

2. If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are

 

 (a) concentric circles

(b) elliptical in shape

(c) straight lines parallel to each other

(d) concentric circles near the point O but of elliptical shapes as we go away from it

3. A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to

(a) A

(b) B
(c) A if the current is small, and B if the current is large

(d) B if the current is small and A if the current is large

4. For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is

(a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid

(b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil

(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet

(d) The N- and S-poles exchange position when the direction of current through the solenoid is reversed

6. Commercial electric motors do not use

(a) an electromagnet to rotate the armature

(b) effectively large number of turns of conducting wire in the current carrying coil

(c) a permanent magnet to rotate the armature

(d) a soft iron core on which the coil is wound

5. A uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure. In the field an electron and a proton move as shown. The electron and the proton experience

(a) forces both pointing into the plane of paper

(b) forces both pointing out of the plane of paper

(c) forces pointing into the plane of paper and out of the plane of paper, respectively

(d) force pointing opposite and along the direction of the uniform magnetic field respectively

7. In the arrangement shown in there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then

(a) the deflection in the galvanometer remains zero throughout

(b) there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed

 (c) there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction

(d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

8. Choose the incorrect statement

(a) Fleming’s right-hand rule is a simple rule to know the direction of induced current

(b) The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors

(c) The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically

(d) In India, the AC changes direction after every 150 second

9. A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in figure. The direction of magnetic field at a point will be North to South

(a) directly above the wire

(b) directly below the wire

(c) at a point located in the plane of the paper, on the north side of the wire

(d) at a point located in the plane of the paper, on the south side of the wire

10. The strength of magnetic field inside a long current carrying straight solenoid is

(a) more at the ends than at the centre

(b) minimum in the middle

(c) same at all points

(d) found to increase from one end to the other

11. To convert an AC generator into DC generator

(a) split-ring type commutator must be used

(b) slip rings and brushes must be used

(c) a stronger magnetic field has to be used

(d) a rectangular wire loop has to be used

12. The most important safety method used for protecting home

appliances from short circuiting or overloading is

(a) earthing

(b) use of fuse

(c) use of stabilizers

(d) use of electric meter

Physics sample Paper 2

        1.  The voltage – current (V – I) graph of a metallic conductor at two different temperature T1 and T2 is shown below. At which temperature is the resistance higher?

 

2. In the circuit diagram shown, the two resistance wires A and B are if same area of cross section and same material, but A is longer than B. Which ammeter A1 or A2 will indicate higher for current? Give reason.

 3. A student while studying the force experienced by a current carrying conductor in a magnetic field records the following observations.
(i)       The force experienced by the conductor increases as the current is increased.
(ii)      The force experienced by the conductor decreases as the strength of the magnetic field is increased.
Which of the two observation is correct and why?

4.  How would the reading of voltmeter (V) change if it is connected between B and C? Justify your answer.

  

5.  What would be the reading of ammeter and voltmeter in the given circuit?

6.  Two conducting wires of same material, equal length and equal diameter are first connected in series and then in parallel. Compare the equivalent resistance in two cases.

7.  What change in the deflection of the compass needle placed at a point near current carrying straight conductor shall be observed if the –
(a)    Current through the conductor is increased?
(b)    Direction of current in the conductor is reversed?
(c)    Compass is moved away from the conductor?

8.  What are magnetic field lines? List any two characteristics of field lines. Draw the pattern of magnetic field of lines due to a current carrying circular loop.

9.  Draw the schematic diagram showing common domestic circuit.

10. State the function of an earth wire? Why is it necessary to earth metallic appliances such as an electric iron?

Physics sample paper 1

SAMPLE QUESTION PAPER 1

1. You have two metallic wires of resistances 6 ohms and 3 ohms. How will you connect these wires to get the effective resistance of 2 ohms? 

2. Calculate the electrical energy consumed by a 1200 W toaster in 20 minutes.

3. State Ohm's Law. Write a mathematical expression for it.

4. No two magnetic field lines interest each other. Explain.

5. What precautions should be taken to avoid the overloading of domestic electric circuits?

6. An electric oven of 2KW power rating is operated in a domestic electric circuit (220V), that has a current rating 5 A. What result do you expect? Explain.

7. A piece of wire of resistance 20 ohms is drawn out so that its length is increased to twice its original length. Calculate the resistance of the wire in the new situation.

8. Study the following circuit and answer the following questions.

   (i) State the type of combination of the two resistors in the circuit.
   (ii) How much current is flowing through
      (a) 10 ohms and through
      (b) 15 ohms resistors
   (iii) What is ammeter reading?

9. A positively charged particle projected towards west is deflected towards north by a magnetic field. What is the direction of the magnetic field?

10. Draw the magnetic field lines of the field produced due to a current carrying circular loop.

11. State the law used to find the direction of magnetic field around a straight current carrying conductor.

12. (a) What is a solenoid?
      (b) Draw the field lines of the magnetic field through and around a current carrying solenoid.
      (c) Which rule helps to find the force on a current carrying conductor in a magnetic field? State the rule.

MCQs on Physics Practicals

MULTIPLE CHOICE QUESTIONS

1. A cell, a resistor, a key and ammeter are arranged as shown in the circuit diagrams. The current recorded in the ammeter will be

(a) maximum in (i)
(b) maximum in (ii)
(c) maximum in (iii)
(d) the same in all the cases

2. In the following circuits, heat produced in the resistor or combination of resistors connected to a 12 V battery will be

(a) same in all the cases
(b) minimum in case (i)
(c) maximum in case (ii)
(d) maximum in case (iii)

3. Electrical resistivity of a given metallic wire depends upon
(a) its length
(b) its thickness
(c) its shape
(d) nature of the material

4. A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross section of the filament in 16 seconds would be roughly
(a) 10 raise to the power 20
(b) 10 raise to the power 16
(c) 10 raise to the power 18
(d) 10 raise to the power 23

5. Which of the circuit components in the following circuit diagrtam are connected in parallel?

   (a)    R1 and R2 only

   (b)   R2 and V only

   (c)   R1 and V only

   (d)   R1, R2 and V

6. The readings of the current flowing through a conductor and the potential difference across its two ends are shown in the ammeter and voltmeter given below. The resistance of the conductor would be

 (a)    20 ohms

 (b)   5.0 ohms

 (c)    2.0 ohms

 (d)   0.2 ohms

7. To determine the equivalent resistance of a series combination of two resistors R1 and R2, a student arrange the following set up.

Which of the following statements will be true for this circuit? It gives

(a)    Incorrect reading for current I and potential difference V both.

(b)   Correct reading for current I, but incorrect reading for potential difference V.

(c)    Correct reading for potential difference V but incorrect reading for current I

(d)   Correct reading for both V and I

8. What will happen to the current passing through a conductor if potential difference across it is doubled and the resistance is halved?
(a)    Remains unchanged
(b)   Becomes double
(c)    Becomes halved
(d)   Becomes four times

9. In the experiment to study the dependence of current on potential difference across a resistor, a student obtained a graph as shown in the diagram.

The value of resistance of the resistor is

(a)    0.1 ohms

(b)   1.0 ohms

(c)    10 ohms

(d)   100 ohms

10. For the circuits shown in figure I and II the ammeter reading would be:

(a)    1 A in circuit I and 0 A in circuit II
(b)   0 A in both circuits
(c)    1 A in both circuits
(d)   0 A in circuit I and 1 A in circuit II