Fleming’s Left Hand Rule MCQs Quiz | Class 10
Welcome to the Class X Science (Code 086) quiz from Unit IV: Effects of Current on Fleming’s Left Hand Rule. This quiz covers the statement and application of the rule, designed to test your understanding. Attempt all 10 multiple-choice questions, then click ‘Submit Quiz’ to see your score. You can also download a detailed answer PDF for revision.
Understanding Fleming’s Left Hand Rule
Fleming’s Left Hand Rule is a fundamental principle in physics, particularly in the study of electromagnetism. It provides a simple way to remember the relationship between the direction of the magnetic field, the electric current, and the force experienced by a current-carrying conductor in that magnetic field. This rule is crucial for understanding the working of electric motors and other electromagnetic devices.
Statement of Fleming’s Left Hand Rule
The rule states that if you stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular to each other, then:
- The Forefinger points in the direction of the Magnetic Field (B).
- The Middle Finger points in the direction of the Current (I).
- The Thumb points in the direction of the Force (F) or motion experienced by the conductor.
It’s important that these three directions are at right angles to each other for the rule to apply accurately.
Application of Fleming’s Left Hand Rule
The primary application of Fleming’s Left Hand Rule is in determining the direction of force on a current-carrying conductor placed in a magnetic field. This phenomenon is known as the motor effect. This rule is universally applied in understanding and designing various electrical devices:
- Electric Motors: In an electric motor, a coil carrying current is placed in a magnetic field. The rule helps predict the direction of force on each side of the coil, leading to its rotation.
- Galvanometers: Used to detect and measure small electric currents.
- Actuators: Devices that convert electrical energy into mechanical energy.
- Loudspeakers: The current in a coil placed in a magnetic field experiences a force, causing it to vibrate and produce sound.
The force experienced by the conductor is maximum when the direction of current is perpendicular to the direction of the magnetic field. If the current is parallel to the magnetic field, no force is experienced.
Summary Table: Finger Mapping
| Finger | Represents | Symbol |
|---|---|---|
| Thumb | Direction of Force/Motion | F |
| Forefinger | Direction of Magnetic Field | B |
| Middle Finger | Direction of Current | I |
Quick Revision Points
- Fleming’s Left Hand Rule relates force, magnetic field, and current.
- It is used when a current-carrying conductor is placed in a magnetic field.
- Thumb = Force, Forefinger = Field, Middle Finger = Current.
- Main application is in electric motors and the motor effect.
- The three directions must be mutually perpendicular.
- Reversing current or field reverses the force.
Practice Questions
- What is the primary purpose of Fleming’s Left Hand Rule?
- Which physical quantity is represented by the forefinger in Fleming’s Left Hand Rule?
- Name one electrical device that operates based on the principle explained by Fleming’s Left Hand Rule.
- If the magnetic field is directed into the page and the current flows from left to right, in which direction will the conductor experience force according to Fleming’s Left Hand Rule?
- What happens to the direction of force if both the direction of the magnetic field and the direction of the current are simultaneously reversed?
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