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B.Tech EEE Magnetism — practice questions — page 2

Explore 72 free Magnetism questions in B.Tech EEE Electrical Engineering. Open each question or exercise to read its content, reference answers and available explanation.

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Magnetism questions and exercises with answers

Showing questions 31–60 of 72.

Amplifiers in microwave ovens use a magnetic field for which purpose?Read the answer and worked solution →A magnetic field is applied across a current-carrying strip and a voltage appears across its width. What is this effect called?Read the answer and worked solution →Who discovered the Hall effect, and in which year?Read the answer and worked solution →Charges move at speed v across a conductor of width l, with B, v and l mutually perpendicular. What is the Hall emf?Read the answer and worked solution →A Hall flow probe on an artery applies a 0.100 T field. The vessel is 4.00 mm across and blood moves at 20.0 cm/s. What Hall emf appears?Read the answer and worked solution →A Hall probe is one of the most common instruments built on the Hall effect. What does it measure?Read the answer and worked solution →A Hall probe measures flow in a pipe of salty water. What decides the sign of the voltage it reads?Read the answer and worked solution →In 1980 a further discovery was made about the Hall effect. What was it?Read the answer and worked solution →A straight wire of length l carries current I in a uniform field B, at an angle theta between the current and the field. What is the magnetic force on it?Read the answer and worked solution →A wire carries 20.0 A through a 1.50 T field, perpendicular to it, with 5.00 cm of its length inside the field. What force acts on it?Read the answer and worked solution →A long wire carries current I through a uniform field B at an angle theta. What is the magnetic force per unit length of the wire?Read the answer and worked solution →Right hand rule 1 is applied to a current-carrying wire in a magnetic field. Where does the thumb point?Read the answer and worked solution →The magnetic force acts on charges drifting inside a wire, yet the whole wire is pushed sideways. Why?Read the answer and worked solution →Which hot, chemically active liquid used in some nuclear reactors is named as well suited to magnetic pumping?Read the answer and worked solution →What is given as the practical drawback of magnetohydrodynamic drives as they exist today?Read the answer and worked solution →A 100-turn square loop 10.0 cm on a side carries 15.0 A in a 2.00 T field. What is the maximum torque on it?Read the answer and worked solution →A rectangular current loop in a uniform magnetic field feels a torque. What is the net force on the loop?Read the answer and worked solution →A motor coil rotates until the perpendicular to the loop lines up with the field. What is the torque at that instant?Read the answer and worked solution →A motor coil coasts past the position of zero torque and nothing else is changed. What does the torque then do?Read the answer and worked solution →For which loop shapes does the torque expression built from N, I, A and B hold good?Read the answer and worked solution →Right hand rule 2 gives the field around a current. How are the thumb and fingers used?Read the answer and worked solution →What is the magnetic field strength at a shortest distance r from a long straight wire carrying current I?Read the answer and worked solution →What is the value of the permeability of free space?Read the answer and worked solution →How much current must a long straight wire carry to create a field of 1.0 x 10^-4 T at a distance of 5.0 cm from it?Read the answer and worked solution →What is the magnetic field strength at the centre of a single circular loop of radius R carrying current I?Read the answer and worked solution →A solenoid has n turns per unit length and carries current I. What is the field strength inside it?Read the answer and worked solution →A solenoid 2.00 m long has 2000 loops and carries 1600 A. What is the field strength inside it?Read the answer and worked solution →Where is the field of a current-carrying solenoid uniform, and where is it almost nothing?Read the answer and worked solution →Which law states the direction and magnitude of the field due to each single segment of a current?Read the answer and worked solution →The law of Ampere is itself part of which larger set of equations?Read the answer and worked solution →

Worked practice questions

Amplifiers in microwave ovens use a magnetic field for which purpose?

  1. To heat the metal oven walls
  2. To hold the oven door closed
  3. To measure the food temperature
  4. To contain oscillating electrons
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Correct answer: D. To contain oscillating electrons

1. Magnetic fields are widely used to contain charged particles. 2. In a microwave oven the amplifier uses a magnetic field to contain oscillating electrons. 3. Those oscillating electrons generate the microwaves that are sent into the oven. 4. Heating the walls or holding the door would need no magnetic containment of charges at all. _Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.5 Force on a Moving Charge in a Magnetic Field: Examples and Applications_

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A magnetic field is applied across a current-carrying strip and a voltage appears across its width. What is this effect called?

  1. The Tesla effect
  2. The Hall effect
  3. The Curie effect
  4. The pinch effect
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Correct answer: B. The Hall effect

1. The magnetic force pushes the moving charges toward one side of the conductor. 2. That leaves a net opposite charge on the other side, so a voltage appears across the width. 3. Creating a voltage across a current-carrying conductor with a magnetic field is the Hall effect. 4. The pinch effect is the squeezing of parallel currents together and is a different phenomenon. _Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.6 The Hall Effect_

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Who discovered the Hall effect, and in which year?

  1. Edwin Hall, in 1979
  2. Hans Oersted, in 1879
  3. Nikola Tesla, in 1897
  4. Edwin Hall, in 1879
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Correct answer: D. Edwin Hall, in 1879

1. The effect is named after Edwin Hall, an American physicist. 2. He discovered it in 1879. 3. Oersted worked half a century earlier on the deflection of a compass needle by a current. 4. The year 1980 belongs to a later discovery, that the Hall effect is quantized. _Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.6 The Hall Effect_

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