AC and DC Current Fundamentals

Answer is B.

The advantage of AC over DC is that power transmission is simpler under AC, it can be changed in voltage relatively easily using transformers, and that higher power motors can be devised under AC. It contains more electric energy.

In A.C, voltage can be increased or decreased with the help of a transformer. But in D.C, this cannot be done. Voltage may be increased using a step up transformer and may be decreased using a step down transformer.

Answer is B.

AC electricity alternates back-and-forth in direction 50 times per second, according to the electrical system in the country. The charge at the ends of the wire alternates between negative (-) and positive (+). If the charge is negative (-), that pushes the negatively charged electrons away from that terminal. If the charge is positive (+), the electrons are attracted in that direction. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position. But if the split ring commutators are attached to the coil then the current will move in the same direction.

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

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.

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.

The frequency of the AC source is 50 Hz, meaning the time period is T = 1/50 = 0.02 s. The given time interval is 0.01 s, which is exactly half of the time period (a half cycle). The average of a sinusoidal voltage over a full cycle is zero, but over a half cycle starting from zero, the average voltage is non-zero (2V_0/pi). However, depending on the exact phase of the 0.01s interval, the average can be zero (e.g., from peak to peak). Thus, it may be zero.

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. 

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

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

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. 

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

Answer is B.

The RMS (Root mean square) value tells us what equivalent DC voltage we would need to get the same power, for the neon bulb to glow.
In this case, the neon bulb glows at 50 V ac voltage. Therefore, for the bulb glow with dc voltage, $50\times \sqrt { 2 } \quad =\quad 50\times 1.414\quad =\quad 70\quad V$ dc voltage should be applied.
Hence, the neon bulb will flash at 70 V dc.

Needle of galvanometer shows magnitude and direction of current through it. In AC, both are continuously changing periodically and this behavior is observed in the needle. 

Alternating currents are:

Direct current never changes its direction it  have magnitude only but the alternating current is of the form: $I _0Sin \omega t$ which have magnitude and as well as direction.

In electrolysis the ionization of the electrolyte takes place where the positive and negative charges move towards opposite electrodes. For this the electrodes are required to be maintained at opposite polarity as long as the process continuous which is possible while supplying a dc current. But if we pass an ac current the polarity of the electrodes will be continuously changing and the ions will not be attracted towards any particular electrode resulting in no ionization. Hence electrolysis cannot take place with ac current.

Electrochemical cells produce DC.

Transmission losses are given as $I^2R$. In AC, voltage transformation to higher(and also lower) values is easier at constant power. So, voltage is increased before transmission reducing current and hence reducing transmission losses.