Answer:
False
Step-by-step explanation:
J. J. Thomson conducted an experiment which lead to the discovery of negatively charged particles only. He took a discharged tube and passed high voltage current through the gas and noticed that some particles from cathode is being emitted. They are fast moving particles and are deviated in the electrical and the magnetic field.
J. J. Thomson did not conclude anything about the positive charge. Hence, the statement is false.