Question 1 :
The magnetic field due to a circular wire at its center is:
Question 3 :
If a straight wire carrying a current $i_{1}$ amp runs along the axis of a circular current carrying loop having current $i_{2}$ amp, then the force of interaction between the two current carrying conductors is
Question 5 :
A solenoid of inductance 2H carries a current of $1 A$. What is the magnetic energy stored in a solenoid?
Question 6 :
No net force acts on a rectangular coil carrying a steady current when suspended freely in a uniform magnetic field.
Question 7 :
In the statement of Fleming's left hand rule, what do thedirection of centre finger represents
Question 8 :
In cyclotron, for a given magnet, radius of the semicircle traced by positive ion is directly proportional to__________. (v=velocity of positron ion)<br/>
Question 10 :
When the current through the electromagnet of a relay reaches a particular value<br>
Question 12 :
In a DC generator, the ends of the coil are connected to __________.
Question 13 :
A neon lamp is connected to a voltage a.c. source. The voltage is gradually increased from zero volt. It is observed that the neon flashes at $50 V$. The a.c, source is now replaced by a variable dc source and the experiment is repeated. The neon bulb will flash at ?<br/>
Question 14 :
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. The total current taken from the supply is :
Question 16 :
Assertion: If the current in a solenoid is reversed in direction while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.
Reason: Magnetic field energy density is proportional to square of current.
Question 17 :
A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x > 0 is now bent so that it now lies in the $y-z$ plane.
Question 18 :
A solenoid of $0.4 m$ length with $500$ turns carries a current of $3 A$. A coil of $10$ turns and of radius $0.01 m$ carries a current of $0.4 A$. The torque required to hold the coil with its axis at right angles to that of solenoid in the middle point of it is:
Question 19 :
A long solenoid has 200 turns per cm and carries a current i.The magnetic field at its centre is $6.28\times 10^{-2}Wb/m^{2}$. Another long solenoid has 100 turns per cm and it carries a current i/3.The value of magnetic field at its centre is:<br/>
Question 20 :
Two heaters A and B are in parallel across the supply voltage. Heater A produces $500 kJ$ in $20$ minutes and B produces $1000 kJ$ in $10$ minutes. The resistance of A is $100 \Omega$. If the same heaters are connected in series across the same voltage, the heat produced in $5$ minutes will be:
Question 21 :
When the electric resistance are connected in parallel, which one of the following quantities is not affected ?
Question 24 :
An electric bulb of $30\ W$ consumes $0.72$ units of energy in a day. Find the number of hours it is working in a day?
Question 25 :
A typical thermistor can easily measure a change in temperature of the order of
Question 26 :
A piece of copper and another of germanium are cooled from room temperature to 80K. The resistance of
Question 27 :
Identify the changes in a circuit on adding a light bulb in parallel to the actual resistance of the circuit. It will:<br/>
Question 28 :
The resistance of a hot tungsten filament is about $10$ times the cold resistance. What will be the resistance of $100\ W,\ $ <br> $200\ V$ lamp when not in use?
Question 29 :
An electric heater of resistance $6\ \Omega $ is run for $10\ min$ on a line of $120\ V$. The energy liberated in this period of time is:<br/>
Question 31 :
A wire of length $5\ m$ and radius $1\ mm$ has a resistance of $1\ ohm$. What length of the wire of the same material at the same temperature and of radius $2\ mm$ also have a resistance of $1\ ohm$
Question 32 :
A unit charge is rotated around a charge of q in a circular path at the distance of r. Then, work done will be:
Question 33 :
Two copper wires whose masses are 8 and 12gm have lengths in the ratio $3:4$. Theirresistances are in the ratio.<br><br>
Question 35 :
An electric toaster draws $8\ A$ current in a $220\ V$ circuit. It is used for $2\ hr$. What is the cost of operating the toaster if the cost of electrical energy is $Rs.\ 4.5 / kWh$?
Question 36 :
Find the electric field in the copper wire of area of cross section $2\ mm^2$ carrying a current of $1\ A.$ The resistivity of copper is $1.7\times 10^{-8}\Omega m$.<br>
Question 37 :
Which of the following is the best conductor of electricity ?
Question 38 :
A material $\mathrm{B}$' has twice the specific resistance of $\mathrm{A}'$. A circular wire made of $\mathrm{B}$' has twice the diameter of a wire made of $\mathrm{A}'$. Then for the two wires to have the same resistance, the ratio $P_{\mathrm{A}}/P_{\mathrm{B}}$ of their respective lengths must be <br/>
Question 39 :
A copper tube is of internal radius 4 mm and outer radius 5 mm. Its resistance is R$_{1}$. The tube is filled with a suitable copper wire. The resistance of the arrangement is R$_{2}$.Then R$_{2}$/R$_{1}$ is<br>
Question 40 :
An electric motor operating on $50 V$ D.C. supply draws a current of $10 A$. If the efficiency of the motor is $40\%$, then the resistance of the winding of the motor is:<br/>
