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SubjectsPhysics
वैद्युतस्थैतिक विभव और विभव ऊर्जा
In this Class 12 Physics topic from Electrostatic Potential and Capacitance, students learn how electric potential describes the work done per unit charge in bringing a test charge from infinity, and how potential difference relates to energy transfer in an electric field. The topic covers potential due to point charges and charge systems, superposition, equipotential surfaces, and the potential energy of charges. Students also connect potential with electric field and build the foundation needed to understand capacitance and capacitors.
TOPIC PRACTICE
Up to 3 questions from this page. Select your focus, then start.
The potential energy of a dipole in a uniform electric field is U = −pE cos θ. Here cos 60° = 1/2, so U = −6 × 7 × 1/2 = −21 J. Therefore option C is correct. The negative sign shows that this orientation has lower energy than the perpendicular orientation; zero would occur at 90°, while −42 J omits the cosine factor.
Use U = −pE cos θ for the potential energy of a dipole. Since cos 120° = −1/2, U = −4 × 9 × (−1/2) = +18 J. Thus option D is correct. The two negative signs cancel because the angle is obtuse. Zero would require 90°, and 36 J incorrectly ignores the factor of one half.
For a dipole, U = −pE cos θ. The product pE is already given as 30 J, and cos 30° = √3/2. Therefore U = −30 × √3/2 = −15√3 J, making option A correct. The positive value misses the required negative sign, −15 uses the wrong trigonometric value, and zero would be valid only at 90°.
QUIZ COMPLETE
