Case Study:

Fourteen-year-old Aarav had been suffering from severe headaches after a sports injury. The doctor advised an MRI scan to check whether there was any internal damage in his brain. Aarav was surprised when he saw a huge machine that could “see” inside his body without any surgery or cuts.

If you're wondering how a simple wire starts acting like a magnet the moment you flip a switch, check out our guide on how electricity creates magnetism. It’s the foundational 'magic' that makes MRI technology possible.

An MRI (Magnetic Resonance Imaging) machine works using very strong magnetic fields produced by electricity. Inside the machine are long coils of wire. When electric current passes through these coils, they behave like powerful electromagnets and create a strong magnetic field around the patient’s body. This magnetic field helps doctors obtain detailed images of organs and tissues.

MRI machines are essentially giant, sophisticated versions of the magnets we use in scrap yards or bells. You can explore more everyday uses of electromagnets to see how this principle runs our modern world.

During one scan, the MRI machine used a magnetic field strength of nearly 1.5 tesla, which is thousands of times stronger than Earth’s magnetic field. Engineers observed that increasing the electric current through the coils increased the magnetic field strength and improved image clarity. However, excessive heating of wires was also noticed when the current became too high.

Doctors and engineers must carefully control the current flowing through the conducting coils so that the machine produces clear images safely. This shows how the magnetic field due to a current-carrying conductor is not only a scientific concept from the classroom, but also an important principle used in modern medical technology to save lives without surgery.

CASE-BASED QUESTIONS

 MCQs 

Q1. In an MRI machine, the strong magnetic field is mainly produced by:
A. Permanent magnets only
B. Current flowing through coils of wire
C. Earth’s magnetic field
D. Chemical reactions inside the machine

Q2. What will most likely happen if the current through the MRI coils increases?
A. The magnetic field decreases
B. Magnetic field remains unchanged
C. Magnetic field strength increases
D. The coils stop conducting electricity

Struggling to visualize which way the magnetic field goes? We’ve put together some simple tricks for the Right-Hand Thumb Rule that will help you solve these types of questions in seconds.

 Assertion – Reason 

Q3. Assertion (A): MRI machines use electromagnets to produce strong magnetic fields.
Reason (R): A current-carrying conductor produces a magnetic field around it.
A. Both A and R are true, and R is the correct explanation of A
B. Both A and R are true, but R is not the correct explanation of A
C. A is true, but R is false
D. A is false, but R is true

 Application-Based 

Q4. Why are coils of wire used in MRI machines instead of a single straight wire?

Q5. Engineers observed heating in the MRI coils when a very high current was used. What does this suggest about the practical use of electricity in such machines?

 Data/Logic-Based 

Q6. An engineer recorded the following observations during MRI testing:

What conclusion can be drawn from the data?
A. The magnetic field decreases with current
B. The magnetic field is independent of current
C. Magnetic field increases as current increases
D. Current damages the magnetic field

 Case-Based Reasoning 

Q7. A technician accidentally reduces the current flowing through the MRI coils during a scan. How may this affect the scan results?

ANSWER KEY WITH EXPLANATION

A1. B. Current flowing through coils of wire
Explanation: According to NCERT, a current-carrying conductor produces a magnetic field. MRI machines use coils carrying an electric current to create strong electromagnets.

A2. C. Magnetic field strength increases
Explanation: The magnetic field around a conductor becomes stronger when the current increases. This principle is used in MRI machines for clearer imaging.

A3. A. Both A and R are true, and R is the correct explanation of A
Explanation:
Both statements are true. MRI machines work because an electric current flowing through coils produces magnetic fields, forming electromagnets.

A4. Coils produce a much stronger and more concentrated magnetic field than a single straight wire. This helps MRI machines generate clear images of body organs.

A5. Higher current can cause excessive heating in wires. Therefore, engineers must balance strong magnetic fields with safe operating temperatures.

A6. C. Magnetic field increases as current increases
Explanation: The table shows a direct increase in magnetic field strength as current increases. This matches the NCERT principle of magnetic effects of electric current.

A7. Reducing the current will weaken the magnetic field. As a result, the MRI images may become less clear and detailed.

Mastering Case-Based questions takes practice. If you want to test yourself further, grab these Physics Worksheets. For a full exam simulation, try our unsolved practice papers or review the solved papers to see how to frame your answers for maximum marks.

HOTS EXTENSION QUESTIONS

Q1. If engineers want stronger MRI images without increasing wire heating too much, what design changes could they make in the electromagnet system?

Q2. Why would an MRI machine become unsafe if the magnetic field strength is increased beyond a certain limit? Explain using reasoning related to electricity and magnetism.

Still have a nagging question about how MRI gradients work? Head over to our Discuss Forum and ask the community! If you're feeling confident, see if you can top the leaderboard in our Physics Quizzes.

 Going Beyond 
Now that you've seen how magnetism creates images, why not look at the reverse? Discover how power plants use induction to generate the very electricity that powers these MRI machines, or dive into the mechanics of electric motors to see this force in motion.

 Need Help? 
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