Magnetic Fields due to a Current-carrying Conductor
How Electric Current Produce a Magnetic Field
Explain how electric current produces a magnetic field
When the switch is closed an electric current flows through the conductor.
The electric current generates magnetic field around the conductor. This will cause a deflection on the compass needle. The magnetic field around a current-carrying conductor can be shown by means of magnetic field lines.
The Pattern of the Magnetic Field Lines around a Straight Conductor
Identify the pattern of the magnetic field lines around a straight conductor
magnetic field pattern is usually given in a plan view. In the plan
view, the conductor is represented by a circle. A dot in circle shows
that the current is coming out of the plane. A cross the circle shows
that the current is moving into the plane.
strength of the magnetic field on the magnitude of the electric
current. The higher the current, the stronger the magnetic field, and
therefore the greater the deflection. The strength of the magnetic field
decreases as you move further from the conductor. There will be less
deflection as the compass is drawn from the current-carrying conductor.
- Right-hand Grip Rule
- Maxwell’s cork screw rule
Right-hand Grip Rule can be applied to a straight conductor or a
solenoid-carrying an electric current. For a straight conductor, the
Right-hand Grip Rule can be stated as:
the wire carrying the current is gripped by the right hand with the
thumb pointing in the direction of the conventional current (from
positive to negative), the fingers will curl around the wire pointing in
the direction of the magnetic field.”
you wrap your right hand around a solenoid with your fingers pointing
in the direction of convectional current, your thumb point in the
direction of the magnetic North pole.”
a right-hand screw advances in the direction of the current, then the
direction of rotation of the screw represents the direction of the
magnetic field due to the current.”
direction of the force on a current-carrying conductor in a magnetic
field can be determined using Fleming’s Left –Hand Rule.
you hold the index finger, the middle finger and the thumb of your left
hand mutually perpendicular to each other so that the index finger
points in the direction of the magnetic field and the middle finger
points in the direction of current in the conductor, then the thumb will
point in the direction of the force acting on the conductor.”
the direction of force due to two current ’82air-carrying conductors
when the current flowing in the same or opposite direction
two current-carrying conductors are placed side by side close to one
another, the currents in the conductors will interact with the magnetic
fields produced by the two conductors. A force may result depending on
the direction of the two currents.
the currents are flowing in opposite directions, the conductors repel
one another. When the currents are flowing in the same direction, the
conductors attract one another, the conductors attract each other.
the currents flow in the same direction, the magnetic field between the
conductors cancel out, thus reducing the net field. However, on the
outside, the magnetic fields add up, thus increasing the net field.
Therefore, the magnetic field is weaker between the conductors that on
the outside. The resultant force pushes the conductor towards each
the currents are in the opposite directions, the fields between the
conductors add up, while they cancel out on the outside. The field
between them is stronger than on the outside. The resultant force is
toward the outside of each conductor, hence repulsion.
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