Electric Motor Basics

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Questions and Answers

Which of the following devices utilize the electromagnetic force acting on a wire in a magnetic field?

  • Induction cooker (correct)
  • Transistor
  • Electric motor (correct)
  • Capacitor

What is one way to increase the force acting on a wire in a magnetic field?

  • Use a thicker wire
  • Reduce the current in the wire
  • Increase the strength of the magnetic field (correct)
  • Change the material of the wire

Fleming's left-hand rule helps to determine what aspect of the electromagnetic effect?

  • Direction of current
  • Type of circuit used
  • Direction of force (correct)
  • Strength of the magnetic field

Which condition can result in no electromagnetic force acting on a wire carrying current in a magnetic field?

<p>The wire is parallel to the magnetic field lines (A)</p> Signup and view all the answers

What is produced around a conductor when a current flows through it?

<p>Magnetic field (B)</p> Signup and view all the answers

Which device uses a changing electromagnetic force to make a cone vibrate?

<p>Speaker (B)</p> Signup and view all the answers

What kind of particle experiences a force in a magnetic field?

<p>Charged particle (C)</p> Signup and view all the answers

When drawing the left-hand rule, which finger is used to represent the direction of the magnetic field?

<p>Index finger (B)</p> Signup and view all the answers

What happens to the coil in an electric motor when the switch is closed?

<p>The coil starts to spin due to the magnetic field. (A)</p> Signup and view all the answers

How can one make the coil in a motor spin in the opposite direction?

<p>By reversing the direction of the current flow. (D)</p> Signup and view all the answers

What is indicated by the direction of the arrow on a magnetic field line?

<p>The direction of the magnetic field. (C)</p> Signup and view all the answers

What would increase the speed of an electric motor's coil when it is switched on?

<p>Using a stronger magnetic field. (D)</p> Signup and view all the answers

When an electric motor's coil is spun manually and a lamp lights up, what does this indicate?

<p>The coil is generating electricity. (D)</p> Signup and view all the answers

What does the left-hand rule help determine?

<p>The direction of the force on a current-carrying conductor. (B)</p> Signup and view all the answers

What effect does placing a wire carrying current in a magnetic field have on the wire?

<p>It experiences a force in a certain direction. (B)</p> Signup and view all the answers

What would be an effective way to increase the force acting on a current-carrying wire in a magnetic field?

<p>Reduce the distance between the magnetic poles. (B)</p> Signup and view all the answers

Which change would allow an electric motor coil to turn faster?

<p>Increase the strength of the magnetic field (A)</p> Signup and view all the answers

What change can be made to make the coil in a motor turn in the opposite direction?

<p>Reverse the direction of the current flow (D)</p> Signup and view all the answers

What is the useful work done in lifting a load 0.80 m if the force used is 2.5 N?

<p>4.0 J (C)</p> Signup and view all the answers

If the total energy transferred by the motor is 6.0 J, how much useful energy was transferred to lift the load?

<p>2.0 J (C)</p> Signup and view all the answers

What effect does a charged particle experience when it moves into a magnetic field?

<p>It experiences a magnetic force perpendicular to its motion (D)</p> Signup and view all the answers

Why is the coil in a loudspeaker made of insulated wire?

<p>To avoid short circuits (B)</p> Signup and view all the answers

When the current in a loudspeaker's coil changes direction, what happens to the cone?

<p>It vibrates, producing sound (D)</p> Signup and view all the answers

What does the abbreviation d.c. stand for in electrical terms?

<p>Direct current (B)</p> Signup and view all the answers

Flashcards

Electromagnetic force

A force created by the interaction of a magnetic field and a moving electric charge.

Fleming's Left-hand Rule

A rule used to determine the direction of the force on a current-carrying wire in a magnetic field. It relates the direction of the magnetic field, the direction of the current, and the direction of the force.

Uniform magnetic field

The magnetic field lines are parallel, evenly spaced, and pointing in the same direction, indicating a uniform magnetic field.

Electric motor

A device that uses the electromagnetic force on a current-carrying wire in a magnetic field to produce movement.

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Electric generator

A device that generates electricity by moving a coil of wire in a magnetic field.

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Charged particle in a magnetic field

The magnetic field is perpendicular to the direction of motion of the charged particle. Therefore, the charged particle must be moving and cannot be parallel to the magnetic field for the force to act upon it.

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Magnetic field strength

The strength of the magnetic field. Usually measured in Tesla (T).

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Magnetic field around a conductor

A magnetic field is generated around a conductor when a current flows through it. This field is circular and concentric with the conductor.

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Magnetic force on a charged particle

The force acting on a charged particle moving in a magnetic field is perpendicular to both the direction of the particle's motion and the direction of the magnetic field.

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Direction of current

The direction of the current is from the negative terminal to the positive terminal of the battery.

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What is D.C.

Direct Current (DC) is a type of current where the flow of electric charge is in one direction only.

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Work done

The amount of work done is equal to the force applied multiplied by the distance moved in the direction of the force.

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Why is the coil insulated?

The coil is insulated to prevent the current from flowing through the support structure, ensuring the current stays within the coil.

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Sound frequency

The frequency of the sound produced by a vibrating object is the same as the frequency of the vibration.

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Magnetic force on a wire

The magnetic force on a current-carrying wire is perpendicular to both the direction of the current and the direction of the magnetic field.

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What does the direction of a magnetic field line show?

The direction a magnetic field line points shows the direction that a north pole of a compass would point.

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What is the motor effect?

A force is exerted on a current-carrying wire when it is placed in a magnetic field. The direction of the force is perpendicular to both the direction of the current and the magnetic field.

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What is a magnetic field line?

A magnetic field line is an imaginary line that represents the direction of the magnetic field at a particular point.

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How can you make a coil spin in the opposite direction?

Reversing the direction of the current in the coil will reverse the direction of the magnetic field lines around the coil. This, in turn, reverses the direction of the force on the coil, causing it to spin in the opposite direction.

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How can you increase the force on a current-carrying wire in a magnetic field?

The force on the wire is perpendicular to both the direction of the current and the magnetic field. Increasing the current or the strength of the magnetic field will increase the force.

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How can you determine the direction of the force on a current-carrying conductor in a magnetic field?

The left-hand rule can be used to determine the direction of the force on a current-carrying conductor in a magnetic field. The thumb points in the direction of the force, the first finger points in the direction of the magnetic field, and the second finger points in the direction of the current.

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How can you predict the direction a coil will turn in a simple electric motor?

The coil rotates in a clockwise direction when the switch is closed. The rule that can be used to predict this is the left-hand rule.

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How can you make a coil spin slower in a simple electric motor?

To make the coil spin more slowly, you could reduce the current flowing through the coil. This will reduce the force acting on the coil, causing it to spin more slowly.

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Study Notes

Motor Effect

  • A coil in an electric motor spins when the switch is closed due to the interaction between the magnetic field of the motor and the current in the coil.
  • To reverse the direction of the coil spin, reverse the current or the magnetic field.
  • Increasing the current or strength of the magnetic field will increase the speed of the coil spin.
  • A magnetic field surrounds a current-carrying wire, changing the direction will impact the coil's spin direction.

Magnetic Field Lines

  • Magnetic field lines show the shape of the magnetic field.
  • The direction of the magnetic field lines is indicated by arrows on the lines.
  • The field lines show the direction of force on a current-carrying wire within the magnetic field.

Electric Motor Operation

  • A closed switch allows current to flow, creating a magnetic field around the coil.
  • The interaction between the coil's magnetic field and the external magnetic field causes the coil to rotate.
  • Replacing the cell and switch with a lamp will light the lamp when the coil is spun by hand, as the motion of the coil creates current.
  • To make the motor spin faster, use stronger magnets, or a higher voltage
  • To change the rotation direction, reverse the current or magnetic poles.

Magnetic Field Patterns

  • The direction of an arrow on a magnetic field line indicates the direction of the field.
  • Circular coil's magnetic field pattern is shown with arrows to demonstrate the field's movement.

Electric Motor Rule

  • The rule students use to predict the direction of spin is related to the motor's wire interaction with the magnet.

Left-Hand Rule

  • The left-hand rule is used to determine the force on a current-carrying conductor in a magnetic field.
  • The rule uses the thumb to indicate the direction of force, the first finger to indicate the direction of the magnetic field, and the second finger to describe the direction of the current.

Loudspeaker Operation

  • A coil interacts with a magnet's field to vibrate a cone and create sound.

DC Motors

  • DC stands for direct current.
  • DC motor uses the interaction between a current-carrying coil and a magnetic field.

Electromagnetic Force

  • A wire carrying current in a magnetic field produces an electromagnetic force.
  • The force can be increased by: increasing the current, and increasing the magnetic field strength.
  • The force will be absent when the wire is parallel to the magnetic field.

Applications

  • Electric motors use the production of electromagnetic forces, along with related principles and concepts.

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Motor Effect Past Paper PDF

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