الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Lectures in General Physics
heating elements) is 1.0 m long and
1.0mm 2 in cross-sectional area. It
carries a current of 4.0A when a
2.0V potential difference is applied
between its ends. What is the
conductivity σ, of Nichrome?
7.13) A copper wire and an iron wire
of equal length l and diameter d are
joined and a potential difference V
is applied between the ends of the
composite wire. Calculate (a) the
potential difference across each
wire. Assume that l=10m,
d=2.0mm, and V=100V. (b) Also
calculate the current density in each
wire, and (c) the electric field in
each wire.
7.14) Thermal energy is developed in
a resistor at a rate of 100W when
the current is 3.0A. What is the
resistance in ohms?
7.15) How much current is being
supplied by a 200V generator
delivering 100kW of power?
7.16) An electric heater operating at
full power draws a current of 8A
from 110V circuit. (a) What is the
resistance of the heater? (b)
Assuming constant R, how much
current should the heater draw in
order to dissipate 750W?
7.17) A 500W heating unit is
designed to operate from a 115V
line. (a) By what percentage will its
heat output drop if the line voltage
drops to 110V? Assume no change
in resistance. (b) Taking the
variation of resistance with
temperature into account, would
the actual heat output drop be
larger or smaller than that
calculated in (a)?
7.18) A 1250W radiant heater is
constructed to operate at 115V. (a)
What will be the current in the
heater? (b) What is the resistance of
the heating coil?
Dr. Hazem Falah Sakeek