o Silicon
o Iron
· Rubber
o Steel
o Salt water
298. Induction current opposes the reason causing it. It is the shortest formulation of
o Einstein’s law
· Lentz law
o Biot-Savart law
o Faraday’s law
o Ampere’s law
299. Potential energy of current carrying loop with magnetic dipole moment µ=1Am2 in magnetic field B of 0.1T, when B and µ make angle 600 is
· -0.05J
o -1J
o 1J
o 0.5J
o 0J
300. Paramagnetism is closely associated with
o The torque
o The force exerted by electron dipole moments on each other
· The tendency of electron dipole moments to align with an applied magnetic field
o The exchange force between electrons
o The tendency of electrons dipole moments to align opposite to an applied magnetic field
301. In an electromagnetic wave E0=3*106V/m. B0 equals
o 10T
· 10-2T
o 100T
o 1T
o 10-8T
302. What is an insulator of electricity?
· A material that doesn’t allow the free electrons to easily travel through it.
o A material that protects the free electrons from excess heat
o A material that protects the free electrons from internal energy propagation
o A material that allows the free ions to easily travel through it
o A material that allows the free electrons to easily travel through it
303. Ohm’s law in differential form is
o I={φ1-φ2±ε}/R
o ω=γE2
o I=V/R
o I= ε/(R+r)
· j=γE, where j is a current density, γ is a conductivity
304. The total number of electron states with n=3 and l=1 for an atom is:
o Four
o eight
o two
o ten
· six
305. The thermal conductivity is the analog to:
o Thermal expansion
o Resistivity
o Elasticity
· Diffusivity
o Viscosity
306. On what picture you can see non –uniform electric field?
· 
o 
o 
o 
o 
307. Resistance of metals in classical theory of electric conductivity is caused by
o Collision of free electrons with dislocations or clasters
o Collision of free electrons with impurity atoms in internodes
o Collision of free electrons with each other
o Collision of free electrons with vacancy defects
· Collision of free electrons with ions of crystal structure
308. Which relation defines equipotential surface:
o 
o 
o 
· 
o dφ/dz=const
309. Electric theory of dispersion was evaluated by:
· Lorentz
o Newton
o Einstein
o Minkovsky
o Maxwell
310. Formula for energy density of electric field is
o 
· 
o 
o 
o 
311. Loop is uniformly rotating with angular velocity ω in uniform magnetic field. Loop has N coils and area of the loop is S. Rotating axis lies on loop’s plane and perpendicular to induction. What is the maximal EMF appeared in the loop:
o 
o NBS
o NBS cos(ωt)
o 
· NBSω
312. Current I=1A goes through the inductance with inductivity L=10-3H. What is the magnetic flux through inductance:
o 2·10-10Wb
o 2·10-3Wb
o 4π·10-10Wb
o 0.5·10-3Wb
· 10-3Wb
313. A toaster is rated at 600W when connected to a 120V source. What current does the toaster carry?
o 2A
o 1A
o 3A
o 4A
· 5A
314. Charge carries in metals are
o electrons and holes
· only electrons
o only holes
o positive ions
o negative ions
315. An electrton traveling with speed v around a circle of radius r is equivalent to a current of:
o evr/2
o ev/r
o 2πer/v
o 2πev/r
· ev/2πr
316. The emf inducted in an isolated circuit when the current in the circuit is changing by 10 A/s is 0.3 V. What is the self-inductance?
o 3 mH
o 3 µH
o 30 µH
· 30 mH
o 30 H
317. The magnetic field for a given electromagnetic wave has Bmax = 10-6T. Emax equals
· 3*102 V/m
o 10-8 V/m
o 5 V/m
o 3 V/m
o 100 V/m
318. An electromagnetic field propagates in +x direction. The electric field at a point in space is momentarily oriented in –z direction. The magnetic field at that point is momentarily oriented in
· –y direction
o +y direction
o +z direction
o +x direction
o -x direction
319. In RLC circuit angular frequency of AC source rises. Inductive reactance
o Remains the same
· Increases
o Oscillates about certain value
o Alternates
o Decreases
320. Magnetic flux through closed conducting loop changed from 10Wb to 5Wb in 10ms. The average EMF induced in the loop is
o 50V
o 500V
o -5V
· -500V
321. The magnitude of emf induced in an isolated circuit when the current in the circuit is changing by -10A/s is 0.2 V. What is the self-inductance?
o 2µH
· 20mH
o 20µH
o 20H
o 2mH
322. The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might be due to:
o a large capacitance
o a small capacitance
· a large resistance
o a small resistance
o a large inductance
323. Intrinsic semiconductors are
o Materials doped by impurities
· Pure elemental materials without impurities
o Materials doped by donor impurity
o Materials doped by acceptor impurity
o Any materials
324. In a charge-free region of space, closed container is placed in an electric field. A requirement for the total electric flux through the surface of the container to be zero is that
o The container must be spherical
o The field must be uniform
o The container must be oriented in a certain way
o The container must be symmetric
· The requirement does not exist – the total electric flux is zero no matter what
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