A small resistor (say, a lamp) is usually put in parallel to be current carrying coil of an electromagnet. What purpose does it serve?

A 6 V, 12 W lamp is connected in series with a resistor R and a source of voltage 12 V. What is the purpose of the resistor R?

Answer the following: (a)Define SI unit of current in terms of the force between two parallel current carrying conductors. (b) Two long straight parallel conductors carrying steady currents I_(a)andI_(b) along the same direction are separated by a distance d. How does one explain the force of attraction between them? If a third conductor carrying a current I_(c) in the opposite direction is placed just in the middle of these conductors , find the resultant force acting on the third conductor.

First a set of n equal resistors of R each are connected in series to a battery of emf E and internal resistance R. A current I is observed to flow. Then, the n resistors are connected in parallel to the same battery. It is observed that the current is increased 10 times. What is 'n'?

A conductor AB of length 10 cm at a distance of 10 cm from an infinitely long parallel conductor carrying a current 10A. What work must be done to move AB to a distance of 20cm if it carries 5A?

(a) Derive an expression for the force between two long parallel current carrying conductors . (b) Use this expression to define S.I. unit of current . (c) A long straight wire AB carries a current I.A proton P travels with a speed v , parallel to the wire , at a distance d from it in a direction opposite to the current as shown in the figure . What is the force experienced by the proton and what is its direction ?

An electric lamp of 100 Omega , a toaster of resistance 50 Omega and a water filter of resistance 500 Omega are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances and what is the current through it ?

The capactor C_1 in the figure initially carries a charge q_0 . When the i switch S_1 and S_2 are closed, capacitor C_1 is connected to a resistor R and a second capacitor C_2 , which initially does not carry any charge. (a) Find the charges deposited on the capacitors in steady state and the current through R as a function of time. (b) What is heat lost in the resistor after a long time of closing the switch?

A long straight wire AB carries a current I. A proton P travels with a speed v, parallel to the wire at a distance d from it in a direction opposite to the current as shown in the figure. What is the force experienced by the proton and what is its direction?

A coil is wound on an iron core and looped back on itself so that the core has two sets of clsely wound wires in series carrying current in opposite senses. What do you expect about its self inductance? Will it be large or small?

A series circuit consists of three identical lamps connected to a battery as shown in Fig. 7.13 . when the switch S is closed, what happens (a) to the intensities of lamps A and B , (b) to the intensity of lamp C , ( c ) to the current in the circuit , and (d) to the voltage drop across the three lamps ? Does the power dissipated in the circuit increase, decrease, or remain the same ?