Two parallel wires carrying direct currents in the opposite directions will:
A. Repel each other
B. Rotate perpendicular to each other
C. Have no effect on each other
D. Attract each other
Answer: Option A
Solution (By JKSSB Mock Tests)
According to Ampere's force law, parallel wires carrying currents in the SAME direction create magnetic fields that attract each other. Conversely, parallel wires carrying currents in OPPOSITE directions create magnetic fields that push against each other, causing the wires to repel. Exam tip: 'Same' Attracts, 'Opposite' Repels (reverse of charges!).
Explanation:
Law of reflection: angle of incidence = angle of reflection, both measured from normal. So 30°. If angle with mirror is given, convert to normal. Always equal for smooth surfaces.
Explanation:
Vector equilibrium: three equal forces at 120° form closed triangle. Third force equals magnitude of others, oriented 120° from each. Memory aid: 'Equilibrium: vector sum = 0; symmetric forces ⇒ symmetric angles'. Statics concept frequently tested in competitive exams.
Explanation:
Fuse melts and breaks circuit when current exceeds rating. MCB (Miniature Circuit Breaker) does same but resettable. Switch only turns on/off. Resistor limits current but doesn't break.
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