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NEET PHYSICSEasy

A polythene piece rubbed with wool is found to have a negative charge of 3×10−73 \times 10^{-7} C. The transfer of mass from wool to polythene is:

A

0.7×10−180.7 \times 10^{-18} kg

B

1.7×10−171.7 \times 10^{-17} kg

C

0.7×10−170.7 \times 10^{-17} kg

D

1.7×10−181.7 \times 10^{-18} kg

Step-by-Step Solution

When polythene is rubbed with wool, it gains electrons and becomes negatively charged. To find the mass transferred, first calculate the number of electrons (nn) transferred using quantization of charge q=neq = ne. n=qe=3×10−7 C1.6×10−19 C=1.875×1012n = \frac{q}{e} = \frac{3 \times 10^{-7} \text{ C}}{1.6 \times 10^{-19} \text{ C}} = 1.875 \times 10^{12}. The mass transferred is the mass of these electrons (M=n×meM = n \times m_e). M=1.875×1012×9.1×10−31 kg≈1.7×10−18 kgM = 1.875 \times 10^{12} \times 9.1 \times 10^{-31} \text{ kg} \approx 1.7 \times 10^{-18} \text{ kg}. (See NCERT Physics Class 12, Exercise 1.11).

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