This section consists of 24 multiple choice questions with over all choice to attempt any 20 questions. In case more than desirable number of questions are attempted, only first 20 questions will be considered for evaluation.
Two point charges + 16q and – 4q are located at x = 0 and x = L. The location of the point on X-axis at which the resultant electric field due to these charges is zero, is :
- 8 L
- 6 L
- 4 L
- 2 L
An electric dipole of dipole moment C-m, kept in a uniform electric field of , experiences a torque of 2 Nm. The angle which the dipole makes with the electric field is :
Two students A and B calculate the charge flowing through a circuit. A concludes that 300 C of charge flows in 1 minute. B concludes that 3.125 × 1019 electrons flow in 1 second. If the current measured in the circuit is 5 A, then the correct calculation is done by :
- both A and B
- neither A nor B
The resistances of two wires having same length and same area of cross-section are 2 Ω and 8 Ω respectively. If the resistivity of 2 Ω wire is 2.65 Ω 10-8 Ω-m then the resistivity of 8 Ω wire is :
In a certain region electric field and magnetic field are perpendicular to each other. An electron entersthe region perpendicular to the direction of both and and moves undeflected. The speed of the electron is :
The given figure shows I – V graph of a copper wire whose length and area of cross-section are L and A respectively. The slope of this curve becomes :
- less if the length of the wire is increased
- more if the length of the wire is increased
- more if a wire of steel of same dimension is used
- more if the temperature of wire is increased
Two identical thick wires and two identical thin wires, all of the same material and the same length form a square in three different ways P, Q and R as shown. Due to the current in these loops the magnetic field at the centre of the loop will be zero in case of :
- P and R only
- Q and R only
- P and Q only
- P, Q and R
A circular current carrying coil produces a magnetic field B0 at its centre. The coil is rewound so as to have three turns and the same current is passed through it. The new magnetic field at the centre is :
Which one of the following statements is true ?
- An inductor has infinite resistance in a dc circuit.
- A inductor and a capacitor both cannot conduct in a dc circuit.
- A capacitor can conduct in a dc circuit but not an inductor.
- An inductor can conduct in a dc circuit but not a capacitor.
The magnetic flux linked with a coil is given by = 5t2 + 3t + 16, where is in weber and t in seconds. The induced emf in the coil at t = 5 s will be :
- 53 V
- 43 V
- 10 V
- 6 V
If a charge is moved against a coulomb force of an electric field, then the :
- intensity of the electric field increases
- intensity of the electric field decreases
- work is done by the electric field
- work is done by the external source
A long solenoid carrying current produces a magnetic field B along its axis. If the number of turns in the solenoid is halved and current in it is doubled, the new magnetic field will be :
Question Nos. 45 to 49 are Assertion (A) and Reason (R) type questions. Given below are two
statements labelled as Assertion (A) and Reason (R). Select the most appropriate answer from the
options given below.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
Assertion (A) : A bar magnet experiences a torque when placed in a magnetic field.
Reason (R): A bar magnet exerts a torque on itself due to its own magnetic field.
(A): A bar magnet experiences a torque in magnetic field
= MB sin So, assertion is true
(R): A bar magnet exerts torque due to other's magnetic field (not its own magnetic field)
So, reason is not true.
Assertion (A): In a series LCR circuit connected to an ac source, resonance can take place.
Reason (R): At resonance XL = XC.
(A): When LCR connected to an AC source, LCR circuit shows the resonance at XL XC because not its reason
(R): It is true.
Assertion (A): When a charged particle moves with velocity in a magnetic field , the force on the particle does no work.
Reason (R): The magnetic force is perpendicular to the velocity of the particle.
(A): A positive charged particle enters in magnetic field normally. It makes the circular path.
Assertion (A): Induced emf in two coils made of wire of the same length and the same thickness, one of copper and another of aluminium is same. The current in copper coil is more than the aluminium coil.
Reason (R): Resistance of aluminium coil is more than that of copper coil.
Assertion (A): A transformer is used to increase or decrease ac voltage only.
Reason (R) : A transformer works on the basis of mutual induction.
(A): A transformer is used to increase or decrease AC voltage only (not dc) because AC voltage provides changing in current which produce magnetic flux.
(R): Transformer works on the principle of mutual induction between primary coil and secondary coil.
Both A and R are true but R is not the correct explanation of A.