Which of the following devices is used to compare the relative magnitudes of charges on two given bodies?

Step 1: Analyze the question We need the device that compares the relative magnitudes (sizes) of charges on two bodies. It is a detector and comparer of charge, not a device for producing or transferring charge.

Step 2: Review each option

• A. Ebonite rod: This is a material that gains negative charge when rubbed with fur. It is used to produce charge, not to compare it.
• B. Proof plane: This is a small metal disc on an insulating handle. It transfers a sample of charge from a body to an electroscope. It only carries charge and does not measure or compare it.
• C. Gold leaf electroscope: This detects charge. When a charged body is brought near or touched to the cap, the leaf diverges from the stem. A larger charge produces a larger divergence, so two charges can be compared by how far the leaf rises. It can also test the sign of a charge and whether a body is a conductor or insulator.
• D. Electrophorus: This generates charge repeatedly by induction. It does not compare charges.

Step 3: Solution To compare two charges, you would use a proof plane to take a sample of charge from each body to the electroscope in turn. The electroscope's leaf divergence shows which charge is larger. The comparing is done by the gold leaf electroscope, since the proof plane only helps carry the charge.

Answer: C. Gold Leaf Electroscope

Exam tip: Remember the roles:

• Ebonite rod and electrophorus produce charge.
• Proof plane carries charge.
• Gold leaf electroscope detects and compares charge.