# Questions on Paragraph - Physics

Seema’s uncle was advised by his doctor to have an MRI (Magnetic Resonance Imaging) scan of his brain. Her uncle felt it to be expensive and wanted to postpone it. When Seema learnt about this, she took the help of her family and also approached the doctor, who also offered a substantial discount. She then convinced her uncle to undergo the test to enable the doctor to know the condition of his brain. The information thus obtained greatly helped the doctor to treat him properly.

Based on the above paragraph, answer the following questions:

(a) What according to you are the values displayed by Seema, her family and the doctor?

(b) What could be the possible reason for MRI test to be so expensive?

(c) Assuming that MRI test was performed using a magnetic field of 0.1 T, find the minimum and maximum values of the force that the magnetic field could exert on a proton (charge = 1.6 x 10-19 C) moving with a speed of 104 m/s.

#### Solution

(a)Values displayed by Seema: Care for her uncle, respect for cumulative family decisions, prompt thinking and general awareness about health-related issues

Values displayed by the family: Prompt decision taking

Values displayed by the doctor: Honest diagnosis, understanding other’s financial concerns

(b)The MRI machine consists of costly parts such as magnetic coils, scanner and superconductors. So, the cost of performing an MRI test is high.

(c)The Lorentz force on a charge is

F = qvBsinθ

The maximum force will be exerted on the proton when v is perpendicular to B.

∴ Fmax=qvB = 1.6 x 10-19 x 104 x 0.1 = 1.6 x 10-16 N

Similarly, the least force on the particle will be when v is parallel to the field B.

∴ Fmin = qvBsin0 = 0 N

Concept: Magnetic Force
Is there an error in this question or solution?
2015-2016 (March) All India Set 3 N

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