physics

When a boron atom (3 valence electrons) is positioned in a silicon crystal lattice we obtain a semiconductor of the type: a) P-N b) P c) N d) SB e) No answer is correct.

P

the work done by an ideal gas at constant pressure is given by the term

P*delta V

which of the following quantities is dimensionless ( dimension one ) a)efficiency b)frequency c)volume d)heat capacity

a

which of the following quantities is measured in MWh ( magewatt hour) a)electric volt b)heat c)output power d)electric current

a

Accommodation of the human eye is caused by a) a change in the curvature of the cornea. b) a change of the curvature of the lens. c) a change in the diameter of the pupil. d) shifting the lens along the eye axis. e) No answer is correct.

a change of the curvature of the lens.

Is joul considered SI unit?

no. it is a derived unit

Which of the following phenomena has nothing to do with interference of light? a) "Mirroring" of air above the hot surface of a road b) Dark stripes or lines which can be seen in poorly adhering glass tables c) The coloured pattern which can be seen on water surface polluted by a small amount of diesel oil d) Rainbow colours seen on wings of e.g. a housefly e) No answer is correct.

"Mirroring" of air above the hot surface of a road

A constant current transported an electric charge of 3.6 C through a conductor during 3 minutes. What was the magnitude of the current? a) 0.6 A b) 1.67 A c) 0.02 A d) 0.01 A e) No answer is correct.

0.02 A

Two particles with the same electric charge repulse each other by a force of 1 μN at a distance of 1 m. When we increase their distance by 2 m, the repulsion force must be: a) 2 μN b) 1 μN c) 0.5 μN d) 0.25 μN e) No answer is correct.

0.25 μN

A 4 m long steel wire with a cross-sectional area of 1 mm2 became longer by 2 cm after the application of a certain force. What was the force applied? (The Young's modulus of steel is 200 GPa.) a) 20 000 N b) 10 000 N c) 2 000 N d) 1 000 N e) No answer is correct.

1 000 N

KJ in watt hour

1 Watt hour (Wh) is equal to 3.6 kilojoules (kJ)

A constant direct electric current passes through a solution of CuSO4, which causes deposition of copper on the surface of the cathode. The passage of an electric charge of 96500 C results in the deposition of a) 1 g of copper. b) 96500 g of copper. c) 0.5 mol of copper. d) 1 mmol of copper. e) No answer is correct.

1 g of copper.

Which of the following amounts of substances involves fewer molecules than is the number of molecules present in 1 g of water? a) 1 g of glucose b) 1 g of helium c) 1 mole of hydrogen d) 1 mole of osmium tetroxide e) No answer is correct.

1 g of glucose

What is the right conversion? a) 100 μl = 10^-2 cm3 b) 1 h = 3.6×10^12 ns c) 10 A = 10^11 nA d) 1 kJ = 1 watt-hour e) No answer is correct.

1 h = 3.6×10^12 ns

1 cubic meter water spills on 1 square kilometer. what will be the thikness of the water?

1 um

Which of the following air pressure values represents the average atmospheric pressure at the sea level? a) 100 hPa b) 120 torr c) 1000 mm of the mercury column d) 101 kPa e) No answer is correct.

101 kPa

100 ml to micro meter?

10^5 uL

10^-1 W/m^2 intensity has value of

110 dB

the intensity of sound at a specific place is 10 W/m^2. what is the sound level value in this case?

130 dB

A lens has a dioptric power of +0.5 dioptre. What is the distance (measured from the lens centre) of the point in which rays coming in parallel with the principal axis intersect? a) 0.2 m b) 0.5 m c) 2 m d) 5 m e) No answer is correct.

2 m

what work has done when sloly letting down a 20 kg object into a hole 10 m deep

2000J

1 hour to pico second?

3.6 * 10^15

Faraday's Law

6.02 x 1023 x 1.60 x 10-19 coulombs

torr

760

radioactive decay

A spontaneous process in which unstable nuclei lose energy by emitting radiation

The change in the curvature of the lens that enables the eye to focus on objects at various distances is called

Acommodation

Neutrino

An electronically neutral, subatomic, nearly massless, particle emitted by the fusion reaction within the sun that travels at nearly the speed of light

Ball A moving with horizontal speed 10 ms rolls across the edge of a chasm in the moon. ball B also falls into the same chasm but with zero horizontal speed. what will happend?

At the momoent of landing the speed of ball A will be higher than that of ball B

Isochoric

Constant volume: no work is done.

The physical principle of a spray gun (an airbrush) is the a) Archimedes' principle b) Continuity equation c) Bernoulli's equation d) Pascal's principle e) No answer is correct.

Continuity equation

Find the right form of the law of radioactive decay (t is time, λ is the decay constant, I intensity of radiation, N number of nuclei). a) N = N0.e−λt b) I = I0.eλt c) N0 = N.e-λt d) N = Nt. eλt e) No answer is correct.

N = N0.e^−λt

After moving a normally illuminated area to a quarter of the original distance from a point source of light, the luminous flux incident on the same area increases by a factor of: a) 2 b) 4 c) 8 d) 16 e) No answer is correct.

No answer is correct.

In the photoelectric effect, a) the energy of photons transforms fully into the energy of secondary photons. b) light is emitted from the conductor carrying an electric current. c) the potential energy of electrons transforms into the energy of photons. d) the energy of electric current transforms partly into light photons. e) No answer is correct.

No answer is correct.

Which of the following processes is a desublimation? a) formation of tooth tartar b) formation of deposits on the sea bottom c) formation of ice "flowers" (frostwork) on windowpanes in winter d) fogging up of windows in a damp room e) No answer is correct.

No answer is correct.

What is the frequency of the circular motion of an object moving uniformly when it completes the whole circle in half a second? a) 0.5 Hz b) 0.2 Hz c) 0.5π rad.s-1 d) 4π rad.s-1 e) No answer is correct.

No answer is correct. The correct answer is: 0.25 Hz

microwaves.

Radio waves with the shortest wavelengths and the highest frequencies

buoying up

The buoyant force on an object that is pushed up in the water is greater than the weight of the object.

Hooke's Law

The law stating that the stress of a solid is directly proportional to the strain applied to it.

Ohm's Law

V=IR

what unit is used for electrical power?

VA

What is the true sentence about sound and ultrasound? a) Sound waves are longitudinal in liquids. b) Sound waves are transverse in liquids. c) When transverse sound waves propagate from the air to the water they become longitudinal. d) When transverse sound waves propagate from the water to the air they become longitudinal. e) No answer is correct.

When transverse sound waves propagate from the air to the water they become longitudinal.

p-type semiconductor

a semiconductor that employs positively charged "holes" in the valence band as the charge carriers

A thermocouple is a) a source of electric voltage. b) a temperature-dependent resistor. c) a device utilizing the heat produced by electric current. d) a special type of transistor. e) No answer is correct.

a source of electric voltage.

n-type semiconductor

a substance whose conductivity is increased by doping it with atoms having more valence electrons than the atoms in the host crystal

in a circuit with alternating voltage, the plated of a capcitor

are repulsed with constant force

The state of weightlessness is always present a) at a free fall in a vacuum. b) if there is a vacuum around the test chamber. c) when swimming underwater. d) about 250 km above the ground. e) No answer is correct.

at a free fall in a vacuum.

What group consisting of only base and derived units of the SI system? a)millibar, ampere, candela,lux b) mole. volt. ampere. joule c)torr, joule. newton, ampere d) atomic mass unit, mole,lux,kelvin

b

which of the following quantities is not scalar? a)temperature b)momentum c)potential energy d)pressure

b

in a n-p-n transistor the electrode connect to the p=type semiconductor is called

base

What are scalar quantities?

quantities with only magnitude and not direaction

an elastic compressible object ( like quite heavy ball) is placed on the bottom of a vessel filled with an incompressible liquid.after some lowering of the external pressure acting on the liquid, the object

can ascend to the liquid surface

Isobaric

constant pressure

Isothermal

constant temperature

which qunatity has units [Kg.m^-3]

density mass

The electrostatic force between two charged particles is

directly proportional to the medium permittivity

Which of the following quantities is measured in farads? a) self-inductance b) electric current in electrolytes c) magnetic force d) electric capacity e) No answer is correct.

electric capacity

X-rays

electromagnetic waves with wavelengths shorter than ultraviolet rays, but longer than gamma rays

W.s can be used as a unit of

energy, It is equevalent to Joul

the electric field produced between two close unlikely charged metal plated is

equipotential

a man applies a force of 200n to a cart of mass 100 kg

force=mass*acceleration

What to remmeber when talking about angular velocity?

full circle is measured by 2pie and when time is given it needed to be thpush in seconds ( how many revolutions per second )

The electric potential in a point in space is always a) indirectly proportional to the relative permittivity of the medium. b) directly proportional to the square of permittivity of the medium. c) indirectly proportional to the square of permittivity of the medium. d) directly proportional to the relative permittivity of the medium. e) No answer is correct.

indirectly proportional to the relative permittivity of the medium

The expression V/T (V is the volume of a perfect gas, T is Kelvin temperature, the number of particles does not change) is a constant in a reversible a) isothermal process. b) isobaric process. c) isochoric process. d) adiabatic process. e) No answer is correct.

isobaric process.

what are the units for angular momentum?

kgm^2/s

the term 0.5p.v^2 contained in the Bernoulli's equation represents

kinetic energy of the unit volume of the flowing liquid

Which of the following quantities is a vector? a) frequency b) magnetic flux density (B) c) capacity of a capacitor d) gas pressure e) No answer is correct.

magnetic flux density (B)

SI units

meter, kilogram, second, ampere, kelvin, candela

The frequency of X-rays is always higher than the frequency of a) gamma rays. b) microwaves. c) a radiation with a wavelength above 0.01 nm. d) a radiation with a wavelength below 1 pm. e) No answer is correct.

microwaves.

Which of the following is not an SI unit (base or derived)? a) mole b) farad c) weber d) minute e) No answer is correct.

minute

give 3 examples for vectors

momentum, acceleration, volacity and displacemtent

the total pressure which can be measured 100m under the surface of pure water equals approximately

more than tenfold the value of atmospheric pressure

Adiabatic

no heat exchange

1 tonne is the same as: 100 kg 10^9 ug 10^9ng 10^12pg

non ot them is correct

what heppens to gravity between two objects when the distance increase or decrease?

opposite reaction. when the gravity increase by 100 times, the distance decreases by 10 times. and hahafech

A practical application of the total light reflection can be encountered in a) car headlights. b) laser pointers. c) optical fibers. d) glasses for 3D vision. e) No answer is correct.

optical fibers.

what is the phase shift of a harmonic periodic motion which definitely causes that the oscillating particle will reach the displacement from the equilibrium position equal to the initial displacement?

pi/2 rad

The energy of the electrons in electron orbitals is given mainly by the a) principal quantum number n. b) orbital momentum quantum number l. c) magnetic quantum number m. d) Bohr's radius. e) No answer is correct.

principal quantum number n.

Which group involves only the particles whose trajectory can be easily changed by the action of a magnetic field? a) electron, proton, neutrino b) proton, electron, oxygen ion c) electron, photon, meson d) neutron, proton, electron e) No answer is correct.

proton, electron, oxygen ion

The instantaneous velocity of a harmonic oscillator is given by the equation v = ym.ω.cos(ωt + φ), where ym is the amplitude of oscillations (maximum displacement), ω angular frequency, t time, and φ the initial phase. At the time t = 0 the value v will a) reach a maximum. b) reach a minimum. c) be zero. d) be always positive. e) No answer is correct.

reach a maximum

photoelectric effect

refers to the emission of electrons from a metal when light shines on the metal

Is energy scalar or vector?

scalar

Is pressure a scalar or a vector?

scalar

is surface tension a scalar or a vector?

scalar

In a reversible isobaric compression of a perfect gas, we can find a decrease in its a) temperature and volume. b) volume and pressure. c) pressure and temperature. d) density and pressure.

temperature and volume.

Two trolleys travel without friction on a horizontal surface. They were originally firmly joined but they somehow pushed themselves away. The 1st trolley mass is 8 kg, the mass of the 2nd trolley is 16 kg. After pushing away the trolleys travel in just opposite direction. Before pushing away they were at rest if a) the 1st trolley travelled at a speed of 8 m/s and the 2nd trolley at a speed of 16 m/s. b) the 1st trolley travelled at a speed of 16 m/s and the 2nd trolley at a speed of 32 m/s. c) the 1st trolley travelled at a speed of 16 m/s and the 2nd trolley at a speed of 8 m/s. d) both trolleys travelled at the same speed in opposite direction. e) No answer is correct.

the 1st trolley travelled at a speed of 16 m/s and the 2nd trolley at a speed of 8 m/s.

In a common light microscope a) the objective forms a virtual image. b) the objective forms an upright image. c) the objective forms a real inverted image. d) the eyepiece is a diverging lens. e) No answer is correct.

the objective forms a virtual image.

lets us have a simple pendulum whose mass is concentrated in the distal end. The angular displacement of the pendulum are small. after shortening the cord of the pendulum to one fourth

the period of the swings does not change

Desublimation

the process in which a gas turns directly into a solid

it is true for a body falling free that:

the sum of its kinetic and potential energy does not change

Imagine a water frop floating in the air at a state of weightlessness. If such a drop is divided into small droplets, then uncer otherwise unchanged conditions

the surface tension of the daughter droplets will be greater if compared with the value of the parent drop

A short horizontally oriented outlet tube is attached near the bottom of a revolvable cylindrical vessel full of a perfect liquid. The outlet tube is tangent to the cylinder - see the scheme. When the liquid starts to flow out of the vessel (drop/descent of the level in the vessel and friction are neglected) a) the vessel starts turning and the rotation rate will stabilise at a value equal to the speed of the liquid flowing out. b) the vessel starts turning at an ever growing speed. c) the vessel will not start turning considering the momentum conservation principle. d) the vessel will not start turning considering the energy conservation principle. e) No answer is correct.

the vessel starts turning and the rotation rate will stabilise at a value equal to the speed of the liquid flowing out.

Bubbles have a spherical shape because a) they "try" to have as small a surface as possible due to surface tension. b) they "try" to have as great a surface as possible due to surface tension. c) they lower their surface tension in this way. d) the Pascal's principle holds here. e) No answer is correct.

they lower their surface tension in this way.

The gravitational potential energy formula E = mgh could be used for very precise calculation of the work necessary a) to fly from the Earth to an Earth's orbit. b) to lift an object from a very deep pit with a depth of h to the level of the surrounding ground. c) to lift a particle to any height h in a homogeneous field of gravity. d) to stop meteorites hitting the Earth. e) No answer is correct.

to lift a particle to any height h in a homogeneous field of gravity

A car travels up a ramp 100 m long to a height of 5 m in 20 s. When lifting the car to the same height in 10 s by a special platform, what is the average power of the platform motor in comparison with the motor of a car travelling up the ramp? (Friction and technical problems are neglected.) a) about 6.67-fold smaller b) the same c) 3 times smaller d) twice as great e) No answer is correct.

twice as great

what is ohm?

unit of electrical resistance

what is the angular velocity of abody rotating with uniform motion if it takes tenth a second to complete one revolution?

w=2pi/0.1= 20pi rad

is electric voltage a scalar?

yes