A block of mass 5 kg is pushed against a wall with a horizontal force of 50 N. Coefficient of friction 0.4. The block (g=10) MCQ with Answer and Explanation
Assertion (A): A fuse wire must have a high resistance and a low melting point. Reason (R): This ensures it melts quickly and breaks the circuit when an excessively high current flows.
A.A is true but R is false.
B.Both A and R are true but R is NOT the correct explanation of A.
C.A is false but R is true.
D.Both A and R are true and R is the correct explanation of A.
Explanation:
A fuse is a safety device. It must have a relatively high resistance so that it produces heat quickly when a large current passes through (H = I²Rt). It must have a low melting point so that this heat causes it to melt immediately, breaking the circuit and protecting appliances. Thus, both A and R are true, and R explains A.
Explanation:
Latent heat of vaporization is the heat required to change unit mass from liquid to vapor at constant temperature (boiling point). For water, it's approximately 2260 kJ/kg. Latent heat of fusion applies to solid-liquid transition. Specific heat relates to temperature change without phase change. Thermal conductivity measures heat transfer rate through conduction. Memory aid: 'Vaporization = liquid to gas; fusion = solid to liquid'. This definition-based question tests precise terminology, crucial for thermodynamics sections in competitive exams where distractors often mix phase change terms.
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