Transcript Current Carrying Loop - Hrsbstaff.ednet.ns.ca

Torque on A Current Carrying
Loop
Physics 12 Adv
Force on a Current Carrying Wire
in a Magnetic Field
Take the equation for the force
experienced by a charged particle moving
in a magnetic field and the definition of
current to develop an equation for a
current carrying wire in a magnetic field
F  IB
Torque
We recall that torque
is the cross product of
radius and force
The units are Nm but
are not joules!
The direction is
positive for ccw and
negative for cw
 
  r F

  rF sin 
Torque on a Current Carrying Loop
Galvanometer
The force experience by
a current carrying wire in
a magnetic field can be
used to build a
galvanometer
Based on the length of
wire, the strength of the
field, the tension in the
spring and the current,
different readings are
obtained
Galvanometer
Show that it is imperative that a
galvanometer used as an ammeter must
have negligible resistance compared to
the effective resistance of the circuit and
that a galvanometer used as a voltmeter
must have infinite resistance
Example
You build a circuit that consists of a 15Ω
resistor and a 1.5V battery.
– Determine the current in the resistor
You know place an ammeter is series with
the resistor that has a resistance of 1.0Ω
and a voltmeter in parallel that has a
resistance of 150Ω.
– Determine the new current in the resistor