The magnetic field due to a current in a long straight wire is a fundamental concept in electromagnetism. When an electric current flows through a straight conductor, it generates a magnetic field that encircles the wire. The direction of this magnetic field can be determined using the right-hand rule: if the thumb of the right hand points in the direction of the current, the curled fingers indicate the direction of the magnetic field lines. The strength of the magnetic field decreases with distance from the wire and is directly proportional to the magnitude of the current. This principle is crucial for understanding various applications, including electromagnets and inductors.
What is the direction of the magnetic field around a long straight wire carrying current?
The direction of the magnetic field can be determined using the right-hand rule: if you point your thumb in the direction of the current, your fingers will curl around the wire in the direction of the magnetic field lines.
How does the strength of the magnetic field change with distance from the wire?
The strength of the magnetic field decreases inversely with distance from the wire; as the distance r increases, the magnetic field B decreases.
What happens to the magnetic field if the current in the wire is doubled?
If the current I is doubled, the magnetic field B at a given distance r from the wire also doubles, since B is directly proportional to I.
What is the shape of the magnetic field lines around a long straight wire?
The magnetic field lines around a long straight wire are circular and concentric, centered around the wire.
Can a magnetic field be produced by a wire carrying no current?
No, a magnetic field is produced only when there is an electric current flowing through the wire. A wire with no current generates no magnetic field.
What is the direction of the magnetic field around a long straight wire carrying current?
a) From the wire outward
b) Circular around the wire
c) Linear along the wire
d) Perpendicular to the wire
Answer: b) Circular around the wire
If the current in a wire is doubled, what happens to the magnetic field at a fixed distance?
a) It remains the same
b) It doubles
c) It halves
d) It quadruples
Answer: b) It doubles
What shape do the magnetic field lines take around a long straight wire?
a) Straight lines
b) Circular lines
c) Elliptical lines
d) Spiral lines
Answer: b) Circular lines
What happens to the magnetic field if the current is stopped?
a) It increases
b) It decreases
c) It remains constant
d) It disappears
Answer: d) It disappears
Which rule is used to determine the direction of the magnetic field around a current-carrying wire?
a) Left-hand rule
b) Right-hand rule
c) Ampere's law
d) Faraday's law
Answer: b) Right-hand rule