In the given circuit, A, B, C and D are four lamps connected with a battery of 60V.
Analyse the circuit to answer the following questions.
(i) What kind of combination are the lamps arranged in (series or parallel)?
(ii) Explain with reference to your above answer, what are the advantages (any two) of this combination of lamps?
(iii) Explain with proper calculations which lamp glows the brightest?
(iv) Find out the total resistance of the circuit.
OR
PQ is a current carrying conductor in the plane of the paper as shown in the figure below.
(i) Find the directions of the magnetic fields produced by it at points R and S?
(ii) Given r1> r2, where will the strength of the magnetic field be larger? Give reasons.
(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?
(iv) Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor.
The lamps are in parallel.
Advantages:
1. In parallel connection, if one lamp is faulty, it will not affect the working of the other lamps.
2. They will also be using the full potential of the battery as they are connected in parallel.
In this case, all the bulbs have the same voltage. But lamp C has the highest current.
Hence, for Lamp C, P = 5 
60 Watt = 300 W. (the maximum).
The total current in the circuit = 3 + 4 + 5 + 3 A = 15 A
The Voltage = 60 V
V = IR and hence R = V/I
= 60/15 A = 4 A
OR
(i) The magnetic field lines produced is into the plane of the paper at R and out of it at S.
(ii) Field at S > Field at P
Magnetic field strength for a straight current carrying conductor is inversely proportional to the distance from the wire.
(iii) The current will be going from top to bottom in the wire shown and the magnetic field lines are now in the clockwise direction on the plane which is perpendicular to the wire carrying current.
(iv) Right hand thumb rule. The thumb is aligned to the direction
of the current and the direction in which the fingers are wrapped around the wire will give the direction of the magnetic field.