Force on Dielectric SlabHardQuestion 31553
Question
When a dielectric slab is partially inserted into a capacitor connected to a constant voltage source, the slab experiences a force:
- ARepulsive, pushing it out
- BAttractive, pulling it inCorrect
- CZero
- DOscillating
Correct answer
Attractive, pulling it in
Explanation
With V constant, U = ½CV². As slab goes in, C increases, U increases. The source must supply extra energy. The slab is pulled in to minimise potential energy of field (the system lowers field energy by polarising).