CBSE Class 12-science Answered
What is potential gradient along the wire
Reading of voltmeter
Asked by diyasinha1701 | 31 Jul, 2021, 09:58: AM
Expert Answer
Let k be potential gradient , i.e., voltage per unit length of potentiometer.
Initially with 2V cell alone Null point is obtained at a length 500 cm
Hence we have , 2 V = k × 500 or k = 4 × 10-3 V/cm
After connecting Voltmeter across cell , null point becomes 490 cm .
This is because voltmeter draws small amount of current and acts as high resistance is connected across cell .
Hence , terminal voltage V of cell is given as , V = k × 490 = 4 × 10-3 × 490 = 1.96 Volt
Since voltmeter reads terminal voltage , voltmeter reading is 1.96 V
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Instead of cell , only voltmeter is connected between one end of potentiometer wire and jack,
we get voltage drop beween potentiometer wire end and jack.
When jack is sliding along the potentiometer wire we get a linear graph of Voltage Vs wire length as shown below.
Slope of graph is potential gradient , i.e., voltage per unit legth of potentiometer wire
Answered by Thiyagarajan K | 31 Jul, 2021, 03:22: PM
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