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[Sylar23]

With regards to the deflection of cathode rays by a magnetic field:

Does anybody help me with this "conclusion" question: Assuming that the rays come from the negative electrode, what does the direction of deflection in the magnetic field indicate about their charge.
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[uberturtle]

Refer to J.J Thompson's experiment on deducing whether cathode rays were EM waves or streams of charged particles.

Since they are attracted to the positive terminal in a magnetic field placed in a vacuum chamber it showed that they were a stream of charged particles and that they were negatively charged (opposites attract!).

It is important that this be carried out in a vacuum or else the cathode rays ionise the gas creating ions which are attracted to the positive and negative terminals hence neutralising the charge at these terminals and the cathode ray will pass through undeflected.

hope this helps!