Having trouble with a physics question

[farmin]

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Having trouble with a question on the TPR cracking test 1.
The passage gave this equation: T = 2*pi*m/q/B
18.Increasing the magnitude of the voltage between the dees would have which of the following effects on the period of the particle’s revolutions in the cyclotron?
A.The period would decrease.
B.The period would increase.
C.The period would remain unchanged.
D.No prediction can be made.

Correct answer was C.The period would remain unchanged. But I thought it was A.
Here was my reasoning:
V=Fd/q. If voltage increase, then increase F.
F=qvB. If F increase, then increase B.
T = 2*pi*m/q/B. If B increase, then decrease T.

Here was the explanation:
C. The equation given in the passage for the period T does not involve the magnitude of the voltage; T depends only on the mass and charge of the particle and the strength of the magnetic field. Therefore, since T is independent of V, we can predict that changing V will have no effect on T.

The explanation didn't help. I mean I was thinking just because voltage wasn't in the equation doesn't mean it cant affect stuff. Well... i dunno.

 

[monkeyvokes]

well, isn't V=Fd/q used for determining the force applied on a particle in an electric field?
and F=qvB used for the force applied on a particle in a magnetic field?
I think the confusion might be coming from two different types of forces (though they are similar).
I'm not a physicist though, but I think that could be the problem.
What do you think?

 

[FeinMS]

T = 2*pi*m/q/B

You should know the basic concept of the cyclotron given in the passage. Between the dees, voltage is applied to accelerate the particle. Inside the dees, there's no voltage to accelerate the particle, but there's magnetic force to change the particle's path.

Given the equation above, you should find out what effect would changing the voltage bring. One of the common types of MCAT questions are finding the relationship between one variable and another. This type of question should be solved based on an equation. The question can be tricky so that your "physical intuition" may be wrong. Trust the formula instead of your intuition when you can utilize both. The equation does not include voltage nor velocity (which will be changed by changing the voltage) so you can tell that T is independent of Voltage