# Two Parallel Currents

## Trending Questions

**Q.**a galvanometer of resistance 50 ohm is connected to a battery of 3 V along with a resistance of 2950 ohm in series a full scale deflection of 30 divisions is obtained in the galvanometer in order to reduce this deflection to 20 divisions the resistance in series should be

**Q.**A wire carrying current I has the shape as shown in the figure.

Linear parts of the wire are very long and parallel to X-axis while semi-circular portion of radius R is lying in Y−Z plane. Magnetic field at point O is

- →B=−μ04πIR(πˆi+2ˆk)
- →B=μ04πIR(πˆi−2ˆk)
- →B=μ04πIR(πˆi+2ˆk)
- →B=−μ04πIR(πˆi−2ˆk)

**Q.**Two point charges in air, at a distance of 20 cm from each other, interact with a certain force. At what distance from each other should these charges be placed in oil of relative permittivity 5 to obtain the same magnitude of force of interaction?

- 8.94×10−2 m
- 7.94×10−2 m
- 6.94×10−2 m
- 5.94×10−2 m

**Q.**A galvanometer of resistance 100 ohm gives full deflection for a current of 10^-5 A. The value of shunt required to convert it into an ammeter of range 1 ampere is :- (1) 1 ohm (2) 10^-3 ohm (3) 10^-5 ohm (4) 100 ohm

**Q.**

Two identical metal balls with charges +2Q and -Q are separated by the same distance, and exert a force F on each other. They are joined by a conducting wire, which is then removed. The magnitude of the force between them will now be

**Q.**In the presence of an applied electric field (→E) in a metallic conductor.

- electrons move in the direction of →E.
- electrons move in the direction opposite to →E.
- electrons move in any direction randomly but slowly drift in the direction of →E.
- electrons move randomly but slowly drift in a direction opposite to →E.

**Q.**A dipole of dipole moment p is placed in non-uniform electric field along x-axis. Electric field is increasing at the rate of 1 V per m then the force on dipole is

**Q.**a galvanometer of resistance, G is shunted by a resistance S ohm. to keep the main current in the circuit unchanged the resistance to be put in series with the galvanometer is

**Q.**

What would be the interaction force between two copper spheres each of mass 1 g, separated by distance 1 m, if the total electronic charge in them differed from the total charge of the nuclei by one percent.?

**Q.**Two long straight wires are set parallel to each other. Each carries a current i in the same direction and the separation between them is 2r. The intensity of the magnetic field midway between them is

- Zero

**Q.**(a) Draw a labelled diagram of a moving coil galvanometer. Describe briefly its principle and working.

(b) Answer the following :

(i) Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer.

(ii) Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason.

**Q.**

If a charged particle does not experience any force in a magnetic field, then ________

**Q.**A power transmission line feeds input power at 2300 V to a step-down transformer with its primary windings having 4000 turns. The output power is delivered at 230 V by the transformer. If the current in the primary coil of the transformer is 5 A and its efficiency is 90%. The output current would be

- 45 A
- 30 A
- 15 A
- 20 A

**Q.**a galvanometer , having resistance of 50 ohm gives a full scale deflection for a current of 0.05A the length of a resistance wire of area of cross section 2.97* 10^(-2)(cm^2) that can be used to convert the galvanometer into an ammeter which can read a max. of 5 A current is (specific resistance of the wire =5*10^(-7) ohm m)

**Q.**Sketch a graph which correctly represent variation of electric field E for a dipole at different points among the line connecting the two charges with procedure

**Q.**Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance 5 m between them. If P and Q carry current of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half way between the wires is

**Q.**A square frame of side l carries a current I and produces a magnetic field B at its center, The same current is passed through a circular coil having same perimeter as that of square. The field at the center of the circular coil is B1. Then the ratio B1B is-

- π22
- π22√2
- π24√2
- π28√2

**Q.**

On what factor does the mutual inductance depend between two coils.

Cross-sectional area of the common core

The number of their turns

Permeability of the core

All of these

**Q.**A galvanometer has 36 ohm resistance. If a 4 ohm shunt is added to this, the fraction of current that passes through the galvanometer is- (1) 1/4 (2) 1/9 (3) 1/10 (4) 1/40

**Q.**An electric current is flowing in a very long pin as shown in the figure. The value of magnetic flux density at point O will be-

- μ0i4πR[π+2]
- μ0i4πR[π+1]
- μ0i4πR[π−2]
- μ0i4πR[π−1]

**Q.**A square loop, carrying an eddy current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I1 at a distance d from the conductor as shown in figure. The loop will experience

- a net attractive force towards the conductor
- a net repulsive force away from the conductor
- a net torque acting upwards perpendicular to the horizontal plane
- a net torque acting downwards normal to the horizontal plane

**Q.**A galvanometer of 100 ohm resistance yields complete deflection when 10 mA current flows. What should be the value of shunt so that it can measure currents upto 100 mA ? (1) 11.11 ohm (2) 9.9 ohm (3) 1.1 ohm (3) 4.4 ohm

**Q.**A moving coil galvanometer has following characteristics,

Number of turns = 80, Area of coil =50 mm2, Resistance of coil = 20 Ω, magnetic field = 0.2 T, torsional constant of the suspension wire = 5×10−9 N-m/rad.

Which of the following statements are correct.

- The angular deflection produced due to a potential difference of 0.01 mV is 0.08 div
- Current sensitivity of the device is 160 div/mA
- Voltage sensitivity of the device is 8 div/mV
- All of the above.

**Q.**92.An electric motor operate on 50V supply and current of 12A if the efficiency of motor is 30% what is resistance of winding of motor?

**Q.**48. AB is 1 meter long …wire of 10ohm resistance .the other data are shown in the circuit diagram.Calculate, a)potential gradient along AB and b)length AO of the wire , when the galvanometer shows no deflection. Explain in detail each step

**Q.**An electron and a proton enters into a region of uniform magnetic field at right angles to the field with the same kinetic energy. They describe circular paths of radius re and rp respectively. then-

- re=rp
- re<rp
- re>rp
- re may be less than or greater than rp depending on the direction of the magnetic field

**Q.**

The ratio of forces between two charges placed at a certain distance apart in air and at half the distance apart in medium of dielectric k is

A)1:4k

B)k:4

C)4k:1

D)4:k

**Q.**A charge Q1 is placed at O inside a hollow conducting sphere having inner and outer radii as 10 m and 11 m as shown in the figure. The force experienced by Q2 at P is F1 when Q1 is placed at the center and force experienced by Q2 when Q1 is placed at O is F2. Then F1F2 is equal to

- 1
- (1213)2
- (1312)2
- None of the above

**Q.**A long wire A carries a current of 10 amp. Another long wire B, which is parallel to A and separated by 0.1 m from A, carries a current of 5 amp in the opposite direction to that in A. What is the magnitude and nature of the force experienced per unit length of B

[μ0=4π×10−7weber/amp−m]

- Repulsive force of 2π×10−5N/m

- Repulsive force of 10−4N/m

- Attractive force of 10−4N/m

- Attractive force of 2π×10−5N/m

**Q.**

How do you increase the sensitivity of a meter bridge?