MCQs on Electric Circuits

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01․ When the lead acid cell is fully charged the electrolyte assumes ________________________ appearance.

During the fully charged condition, the electrolyte produces hydrogen and oxygen gases. Due to the formation of hydrogen bubbles in the electrolyte, it gives the electrolyte a milky appearance.

02․ The ratio of ampere-hour efficiency to watt-hour efficiency of a lead acid cell is
just one.
always greater than one.
always less than one.
none of the above.

In watt hour efficiency, we are considered the voltage and current. The discharging voltage is always less than the charging voltage. We know that, the watt hour efficiency is the ratio of the product of discharging voltage and discharging current to the product of charging voltage and charging current. Thus, the overall watt hour efficiency is always less than the ampere hour efficiency.

03․ Open circuit voltage of a fully charged lead acid cell is
1.9 V.
2 V.
2.7 V.
2.5 V.

In a new lead acid battery, under equalizing charge the voltage rises to approximately 2.65 to 2.7 volts per cell.

04․ In a lead acid cell PbSO4 formed during
charging only.
discharging only.
both during charging as well as discharging.
neither during charging nor discharging.

When a lead-acid battery is discharged, the electrolyte divides into H2 and SO4. The H2 will combine with some of the oxygen and that is formed on the positive plate to produce water (H2O). The sulfate (SO4) combines with the lead (Pb) of both plates, forming lead sulphate (PbSO4).

05․ During charging, the electrolyte of a lead acid battery becomes
diluted with water.
there is no change in electrolyte.

During the charging process, the amount of acid content in the electrolyte increases and that makes the electrolyte as stronger.

06․ The value of specific gravity of acid when a lead acid battery is fully charged is

In a fully charged cell, the electrolyte has a specific gravity that varies from 1.260 to 1.285 and it depends on the type and the manufacturer.

07․ The current flowing between electrodes inside a lead acid battery is
electron current.
proton current.
ionization current.
polarization current.

In lead acid battery, the gas evolution rates at both electrodes are increased due to the float polarization. Hence, the current flowing between the electrodes inside the battery is polarization current.

08․ The plates of lead acid storage battery are most likely to be short circuited if
the electrolyte evaporates.
the battery charged too slowly.
sediment collect at the bottom of the battery.
too much water is added.

During charging and discharging, the lead on the plates gets gradually eaten away and the sediment falls to the bottom. This lead sediment is a conductive material and that makes a short circuit in between the positive and negative plates and finally it becomes a full short circuit.

09․ Two sinusoidal quantities are said to be in phase quadrature, when their phase difference is

Two sinusoidal quantities are said to be in phase quadrature, when their phase difference is 90o.

10․ The equation for 25 cycles current sine wave having rms value of 30 amps, will be

General equation of sinusoidal current quantity is Imsinωt = Imsin2πft. Where, Im is the maximum ampletude of the current wave, f is the frequency or cycle per second. Here, rms value of current is 30 A. ∴´ Maximum amplitude of the current wave form Im = √2 × 30 = 42.4 A and frequency f is here 25 Hz. Hence, the current equation will be 42.4sin2π25t = 42.4sin50πt.