The correct answer is: A. always polarized.
A paper capacitor is a type of capacitor that uses two sheets of metal foil separated by a layer of paper. The paper is impregnated with a dielectric material, which is a material that can store an electric charge. The metal foils are then connected to the terminals of the capacitor.
Paper capacitors are usually polarized, which means that they have a positive and a negative terminal. This is because the dielectric material in the paper capacitor has a preferred direction of polarization. When the capacitor is connected to a voltage source, the electric field will cause the dielectric material to align in the direction of the field. This alignment will create a net charge on the metal foils, with the positive charge on one foil and the negative charge on the other foil.
The polarity of a paper capacitor is important to consider when using it in a circuit. If the capacitor is connected to a voltage source with the wrong polarity, it can be damaged.
The other options are incorrect because:
- B. usually of fixed value is incorrect because paper capacitors can be either fixed or variable.
- C. electrolytic condenser is incorrect because electrolytic capacitors are a type of capacitor that uses a liquid electrolyte as the dielectric material.
- D. a variable condenser is incorrect because paper capacitors are usually fixed value capacitors.