Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics optoelectronic devices resistance and temperature

A solid reflects incident light and its electrical conductivity decreases with temperature. The bonding in this solid is :

  1. ionic

  2. covalent

  3. metallic

  4. molecular
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metals reflect incident light by the vibrations of free electrons under the influence of electric field of incident wave. The conductivity of metals decreases with increase of temperature due to increase in random motion of free electrons. The bonding is therefore metallic.

Multiple choice physics optoelectronic devices resistance and temperature

LEDs are better than conventional incandescent power lamps because:

  1. LEDs have higher efficiency.

  2. LEDs look beautiful.

  3. LEDs are cheap.

  4. all of the above.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

LEDs are better than conventional incandescent power lamps because:-

i)LEDs use less power (watts) per unit of light generated (lumens)
ii) LEDs have higher effiiciency.
iii)LEDs have longer lifetime.
iv)LEDs are cheap.
v)LEDs look beautiful.
Hence option D is correct.

Multiple choice physics optoelectronic devices resistance and temperature

A laser device produces amplification in the

  1. Microwave region

  2. Ultraviolet or visible region

  3. Infrared region

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A laser device produces amplification in the Ultraviolet or visible region of the spectrum. 

Multiple choice physics optoelectronic devices resistance and temperature

LASER is an acronym for light amplification by.

  1. Stimulated energetic radiation

  2. Spontaneous emission of radiation

  3. Stimulated emission of radiation

  4. Spontaneous emission of radio waves
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation".

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

From below which are the applications of heating effect of electric current?

  1. Electric immersion water heater

  2. Electric Iron Box

  3. Electric Fuse

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to heating effect of electric current, heat is produced in the materials that have resistance, thus electric immersion water heater, electric iron box and electric fuse are the applications of heating effect of electric current.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Why are bulbs filled with chemically inactive Nitrogen or Argon gas?

  1. To prevent oxidation of Tungsten filament

  2. To prevent dehydration of Tungsten filament

  3. To prevent oxidation of Steel filament

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Bulbs are filled with chemically inactive Nitrogen or Argon gas to prevent the oxidation of tungsten filament used in the bulb.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

An electric fuse used in households works on which principle of:

  1. Joule's heating

  2. Coulomb's law

  3. Maxwell's law

  4. Ohm's law
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An electric fuse in households works on the principle of Joule's heating that heat produced due to the excess current flowing through it melts the fuse wire which cut off the circuit and hence the appliance is prevented from damage.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

Why is electric power transmitted over long distances at high voltage?

  1. To minimize power loses due to Joule's heating

  2. To maximize power loses due to Joule's heating

  3. To balance power loses due to Joule's heating

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For constant electric power, higher the voltage, lower is the current (as $P=IV$) through the wire. As power loss due to Joule's heating is proportional to $I^2$, for a small current, power loss is also small. So, power is transmitted over long distances at high voltage to minimize power loses due to Joule's heating.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

A vertical wire caries a current in upward direction. An electron beam sent horizontally towards the wire will be deflected

  1. towards right

  2. towards left

  3. upwards

  4. downwards
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using Right-Hand thumb rule and (Flemmings Left Hand Rule, current direction (i) = Left Side Magnetic field  (B) = outwards, so the direction of the force is upwards.

Multiple choice physics electric current and its effects coil and fuse heating effect of electric current- uses applications of heating effect of electric current

When a metallic conductor is heated then the atoms in the metal vibrate with ?

  1. low amplitude and frequency.

  2. greater amplitude and frequency.

  3. greater amplitude and low frequency.

  4. less amplitude and greater frequency.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a metallic conductor is heated its atoms get more energy and get agitated. That is why they vibrate with greater amplitude and frequency.