In the circuit shown in the diagram, the current in the solenoid (opening is per
ID: 2095653 • Letter: I
Question
In the circuit shown in the diagram, the current in the solenoid (opening is perpendicular to
the plane of the page) is in the direction shown (counterclockwise). The current is
INCREASING linearly in time.
The battery in the circuit has an emf equal to the emf of a single loop around the solenoid.
The bulbs are all identical and the internal resistance of the battery is much less than the
resistance of the bulbs.
Consider a single light bulb connected to the battery to have brightness 1 B
Consider two bulbs connected in series to the battery to have brightness 2 B .
Consider three bulbs connected in series to the battery to have brightness 3 B , etc.
a) Give the brightness of each bulb for the circuit as shown.
For each of the following
parts, give the brightness of
each bulb when the
indicated change is made.
Take each part
SEPARATELY
Explanation / Answer
(a) As more and more bulbs are added brightness of bulb A becomes more and more similar to the brightness of bulb X.
Reason : Each bulb has its resistance (say R). When more bulbs are connected across B its resistance keeps on decreasing. In the limit it becomes zero(a short-circuit similar to 2nd figure). Hence its brightness becomes like X.
(b) Becomes similar to brightness of bulb Z.
Reason : When more and more bulbs are added, voltage across B becomes V/(n+1), where n is the number of bulbs added. In the limit when n is very large, this values tends to zero. Hence it is similar to connecting a short-circuit across B. Therefore its brightness will resemble that of Z.