Practice portal › Current Electricity › Electric Current and Drift Velocity
A charged particle having drift velocity of 7.5×10⁻⁴ m s⁻¹ in an electric field of 3×10⁻¹⁰ V m⁻¹, has a mobility in m² V⁻¹ s⁻¹ of
Asked in NEET 2020 · Drift velocity, mobility and current density
- (1) 2.25×10¹⁵
- (2) 2.5×10⁶
- (3) 2.5×10⁻⁶
- (4) 2.25×10⁻¹⁵
Answer: (2) 2.5×10⁶
Step-by-step solution
Mobility μ = (v_d)/E.
μ = (7.5×10⁻⁴)/(3×10⁻¹⁰)
μ = 2.5×10⁶ m² V⁻¹ s⁻¹.
Why the other options are wrong
- (1) The 2.25 comes from multiplying v by E, but that product is 2.25×10⁻¹³, so no single slip gives 10¹⁵; mobility is v/E anyway.
- (3) Right mantissa with the exponent's sign flipped: dividing by 10⁻¹⁰ adds 10 to the exponent, giving 10⁶.
- (4) The 2.25 comes from multiplying v by E, but that product is 2.25×10⁻¹³, not 10⁻¹⁵; mobility is v/E.
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