Download - Electromagnetic induction
Electromagnetic Induction
The interaction between current and magnetic field
Remember from Year 12
• When current flows through a wire a magnetic field is created around the wire
• And if the wire is coiled (to form a solenoid)
The relationship between electricity and magnetism (Motor effect)
Just like;
Magnetic Fields
Remember from Year 12
• When a wire moves through a magnetic field a voltage is induced
• Or a magnetic field moves through a coil a voltage is induced
The relationship between magnetism and electricity (Generator effect)
Using Your Hand and Formulae
)θ(sinBILF
BvLV
)θ(sinBqvF
• Right-hand grip rules• Right –hand slap rule
• Force on a current carrying wire (motor effect)
• Induced voltage (generator effect)
• Force on a charge
The Motor Effect
• A current carrying wire at an angle to a magnetic field experiences a force
• This is as a result of the interaction between the magnetic field and the magnetic field around the wire.
Electric Motors
• Most electric motors use electricity to make magnetism
-the motor effectThe use of electric motors is widespread with most of us using many each day
RH Grip Rule -Wire
RH Grip Rule -Solenoid
RH Grip Rule -SolenoidPredict the direction of the North
magnetic pole
RH Grip Rule -SolenoidPredict the direction of the North
magnetic pole
RH Grip Rule -SolenoidPredict the direction of the North
magnetic pole
RH Grip Rule -SolenoidPredict the direction of the North
magnetic pole
RH Motor Rule Examples
I
I
Predict the direction of the force on the wire and label the positive end of
the wire
RH Motor Rule ExamplesI
I
Predict the direction of the force on the wire and label the positive end of
the wire
RH Motor Rule Examples
I
I
Predict the direction of the force on the wire and label the positive end of
the wire
RH Motor Rule ExamplesPredict the direction of the force on
the wire and label the positive end of the wire
RH Motor Rule ExamplesPredict the direction of the forces
on the wire coil at 1 and 2
Force on a Charge
• A single charge or a charged object will also experience a force as it moves through a magnetic field as it too creates a magnetic field as it moves (just like current in a wire)
Force on a Charge
Slap Rule for Force on a Charge
v
v
Force on a Charge
Force on a ChargePredict the direction of the force on
the moving positive charge
+q
Force on a ChargePredict the direction of the force on
the moving positive charge
+
Force on a ChargePredict the direction of the force on
the moving negative charge
-q
Force on a ChargePredict the direction of the force on
the moving negative charge
-
Force on a Charge –the maths
• Force on moving charges in a wire;
• Force on moving charges on their own;
)θ(sinBILF
)(sinBqvF Where;
F=force (N)B= magnetic field strength
(T)q=charge on the object (C)v=velocity of the charge
(ms-1)=angle from field lines ()
Exercises
1. Find the force on an electron (1.60×10-19C) travelling at 3×107 ms-1 perpendicular to a magnetic field of 0.18T
9×10-13N2. Calculate the charge of a particle travelling
at 340ms-1 perpendicular to a 1.2T magnetic field that experiences a force of 3.5×10-12N
8.6×10-15C
Electricity Generation
• Most generators use magnetism to generate electricity
-The generator effect
Induction -the Generator Effect
• A wire that moves through a magnetic field has a voltage induced across it and therefore a current is induced
• Of course the magnetic field can move past the wire and cause induction also
• Induction is the result of the interaction between the magnetic field and the negatively charged electrons in the wire
RH Generator Rule
•To predict the direction of the induced current use the modified RH slap rule•As with the RH slap rule for the motor effect, the thumb is the cause (the velocity of the wire for a generator), the fingers are the field lines, and the “slap” is the direction of the resultant (in this case the current)
v
B
I
RH Generator Rule Examples
v
Predict the direction of the current and label the +ve end of the wire
RH Generator Rule Examples
v
v
Predict the direction of the current and label the +ve end of the wire
vv
RH Generator Rule ExamplesPredict the direction of the current and label the +ve end of the wire