A 40 v d.c. supply is connected to a series combination of two 10 Ω resistor R. The value of R varies from 0 to 20 Ω. A voltmeter of infinite resistance is connected across one of the 10 Ω resistors as shown in the circuit diagram. Which range of value is displayed by the voltmeter when R is varied?
A 40 v d.c. supply is connected to a series combination of two 10 Ω resistor R. The value of R varies from 0 to 20 Ω. A voltmeter of infinite resistance is connected across one of the 10 Ω resistors as shown in the circuit diagram. Which range of value is displayed by the voltmeter when R is varied?
The correct option is A 20 V - 10 V
, the variable
rheostat varies from 0 ohm to 20 ohm. Since all the elements in the circuit are
linear (they produce a straight V vs I curve), the reading of the voltmeter
will also value linearly.
To set the limits of
the voltmeter value, we simply must look at voltmeter reading at both extreme
conditions of rheostat i.e., o and 20 ohm.
At 0 ohm, the
voltmeter reading is 20 V as voltage drop is shared equally between the 10 ohm
resistors.
At 20 ohm, the
voltmeter reading is 10 V as voltage drop now is divided between 3 elements.
As a result, voltmeter
reading varies between 10 and 20 ohm
, the variable rheostat varies from 0 ohm to 20 ohm. Since all the elements in the circuit are linear (they produce a straight V vs I curve), the reading of the voltmeter will also value linearly.
To set the limits of the voltmeter value, we simply must look at voltmeter reading at both extreme conditions of rheostat i.e., o and 20 ohm.
At 0 ohm, the voltmeter reading is 20 V as voltage drop is shared equally between the 10 ohm resistors.
At 20 ohm, the voltmeter reading is 10 V as voltage drop now is divided between 3 elements.
As a result, voltmeter reading varies between 10 and 20 ohm
