Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

Identify the two types of current exist in physics.

  1. direct and alternating

  2. indirect and alternating

  3. direct and attenuating

  4. directive and alternative

  5. none of the answers are correct
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There exists two types of current -  direct current (dc) and alternating current (ac).

Direct current has constant magnitude and direction whereas the alternating current keeps reversing its direction at regular intervals.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

$AC$ and $DC$ can be distinguished using.

  1. heating effect

  2. magnetic effect

  3. chemical effect

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is possible to distinguish the AC and DC using magnetic effect. Both AC and DC can produce magnetic field but only AC can produce a varying magnetic field. So, using DC, current cannot be induced into another conductor. It can only be done using AC.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

A transistor based radio receiver set (effective resistance of the order of 18 ohms) operates on a 9V dc battery. If this replaced by a dc power supply with rating 9V, 500A then:

  1. Receiver will work normally

  2. Receiver will give distorted output

  3. Receiver will get burnt

  4. Power supply will get over heated
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

In this case, the 9 V battery is replaced with a 9 V power supply. Here, there is no change in the power supply to the radio receiver.
Hence, the receiver will work fine as the voltage supply or power supply remains the same.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

Hotwire ammeters are used for measuring _____________ currents.

  1. A.C. only

  2. D.C only

  3. both A.C. and D.C

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hot wire instruments use the Joule’s law of thermal expansion. When a current (AC or DC) is passed through a special wire, the wire heats up due to $(I^2)\times R$ loss. This heating increases the length of the wire. This increase is recorded as the current. The calibrations indicates an aggregate value which goes with both AC and DC measurements. Over usage can tear the wire apart and render it un-usable. These also measure true RMS for an applied AC. 

Hence they are used for measuring both AC and DC.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

If $\vartheta $ is the phase difference and T is time period then time difference between current and voltage is ;

  1. $T \vartheta $

  2. $\dfrac { T }{ \vartheta } $

  3. $\dfrac { 2\pi T }{ \vartheta } $

  4. $\dfrac { T \vartheta }{ 2\pi }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The phase difference theta corresponds to a time difference delta_t. Since 2*pi radians corresponds to one time period T, the ratio is delta_t/T = theta/(2*pi). Thus, delta_t = (T * theta) / (2*pi).

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

The resistance of a coil for dc is $R$ ohms. When connected to ac supply the total resistance offered by circuit to ac current.

  1. Will remain same

  2. Will increase

  3. Will decrease

  4. Will be zero
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Resistance offered by coil is same for $AC$ as well as $DC.$ So, Resistance will not change.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

Consider the following statements:
(a) The magnitude and direction of alternating current reverses periodically.
(b) Frequency of alternating current in india is 50 Hz.
(c) The frequency of direct current is zero.
Which of the above statements are correct?

  1. (b) and (c)

  2. (a) and (b)

  3. All of them

  4. None of them
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electricity flows in two ways: either in an alternating current (AC) or in a direct current (DC).
Electricity or "current" is nothing but the movement of electrons through a conductor, like a wire. The difference between AC and DC lies in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, or "forward." In AC, electrons keep switching directions, sometimes going "forward" and then going "backward." Alternating current is the best way to transmit electricity over large distances. 

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

Choose the correct option

  1. In Direct Current, Magnitude and direction of current is constant

  2. In Direct Current, Magnitude and direction of current reverses periodically

  3. In Alternating Current, Magnitude and direction of current is constant

  4. Direct current is periodic in nature
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Direct current is categorized by current of constant magnitude and direction.