Explanation:
Potentiometer uses null method: at balance, no current flows through cell, so measured voltage equals true EMF (no internal resistance drop). Memory aid: 'Null method ⇒ zero current ⇒ accurate EMF measurement'. Experimental physics concept frequently tested in competitive exams to verify understanding of precision measurement techniques.
Assertion (A): When ice floats in water, its approximately 1/10th volume remains outside the water. Reason (R): The density of ice is approximately 10% less than the density of water.
A.Both A and R are true but R is NOT the correct explanation of A.
B.A is false but R is true.
C.A is true but R is false.
D.Both A and R are true and R is the correct explanation of A.
Explanation:
The density of ice is about 900 kg/m³ (0.9 g/cm³), while pure water is 1000 kg/m³ (1.0 g/cm³). According to the principle of floatation, the fraction of volume submerged is the ratio of densities: ρ_ice / ρ_water = 0.9. This means 90% is submerged, leaving exactly 10% (1/10th) exposed above the surface. Reason R explains Assertion A.
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