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Showing posts with label MCQ. Show all posts
Showing posts with label MCQ. Show all posts

Online test/2021/1-MCQ

 

MULTIPLE CHOICE QUESTIONS

CBSE TERM 1 PRACTICE QUESTIONS

CLASS X

TERM 1

Chapter : Light – Reflection and Refraction

(To download the MCQ pdf - click the link MCQ - Light: reflection and refraction)

To check your score in MCQs, attempt the online test  - Online Test -Light reflection and refraction

Ohm's Law



Ohm's Law is a relationship between potential difference applied across a conductor to the electric current flowing in it.

You must have experienced the following situations in daily life:

(1) Fluctuations in voltage which leads to dimming or brightening of electric bulb. (This is the reason why we use stabilizers for ACs - to prevent any damage due to voltage fluctuations ) 
(2)  While playing with LEDs, torch bulb, electric cells and connecting wires you must have observed that by increasing the number of cells in the circuit the LEDs glows brighter.
(3) A 12V battery provides a large amount of current than a 3V battery.

This suggests that there must be a relation between voltage (potential difference) and electric current. This relationship is known as Ohm's Law.

Ohm's law was given by George Simon Ohm in the year 1827. This is a relation between potential difference (V) applied across the ends of a conductor to the electric current (I) flowing in the conductor

According the Ohm's Law, the electric current flowing in a conductor is directly proportional to the potential difference (V) applied across the ends of a conductor provided the temperature of the wire remains the constant.

Mathematically,
                              I    ∝    V
or it can also be written as

                            V  ∝    I
removing the proportionality sign and introducing a constant

                            V   =  R I

Where R is a constant known as the resistance of the given conductor.


Graph:



The V–I graph is a straight line that passes through the origin of the graph, as shown in Figure. Thus,
\[\frac{V}{I}\]
is a constant ratio.


Resistance

Physically, resistance is defined as a property of a conductor to resist the flow of charge through it.

The SI unit of resistance is ohm (Ω)  (Greek symbol omega)

A conductor is said to have a resistance of 1Ω when a potential difference of 1V is applied across the ends of a conductor and a current of 1A flows through it.
\[R=\frac{V}{I}\]
\[1Ω=\frac{1V}{1A}\]

A fan regulator is actually a variable resistor. It changes the resistance of the circuit and thereby we can control the speed of the fan.

To test your knowledge on Ohm's Law, attempt the following test.
you will get your score immediately. 


Click the link below to attempt the test:


Some more questions on Ohm's Law:

1. Name and state the law which relates the current in a conductor to the potential difference across a conductor and the current flowing through it.

2. Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

3. When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.


4. (a) How much current will an electric bulb draw from a 220 V source, if the resistance of the bulb filament is 1200 Ω? (b) How much current will an electric heater coil draw from a 220 V source, if the resistance of the heater coil is 100 Ω?

5. The potential difference between the terminals of an electric heater is 60 V when it draws a current of 
4A from the source. What current will the heater draw if the potential difference is increased to 120 V?


6. The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below –

I (amperes) 0.5    1.0     2.0      3.0       4.0
V (volts)     1.6    3.4     6.7     10.2     13.2
Plot a graph between V and I and calculate the resistance of that resistor.


7. Keeping the potential difference constant, the resistance of a circuit is doubled. By how much does the current change?






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

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