MCQs on Electric Circuits

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01․ The greater the internal resistance of a cell
the lesser the emf.
the lesser the terminal voltage.
the greater the emf.
the greater the terminal voltage.

The terminal voltage is the difference between the source voltage and the voltage drop due to the internal resistance. So, if the internal resistance increases, then the overall terminal voltage also reduces according to the above expression.

02․ A external resistance R is connected to a cell of internal resistance r, then the current is maximum when
R < r.
R > r.
R = r.
none of the above.

The external resistance (R) is connected with the internal resistance (r) of the cell in series connection. So, the total resistance is ( R + r ). When the total resistance is low, then there is a maximum current flow in that circuit. If we apply the option (A) and (B), then the overall resistance increases than the option (C). Hence, if the external resistance (R) and the internal resistance (r) are equal, then the maximum current flows through the circuit.

03․ When the internal resistance of a cell is large compared to the external resistance in the circuit then high current can flow through the external resistance by grouping the cells
as in series.
in parallel.
in either series or parallel.

As per the above statement, the internal resistance of the cell is larger than the external resistance. So, if we connect the cells in parallel, then the overall internal resistance decreases. We know that, in low resistance path the current flow is more. Hence, we need to group the cells in parallel to make the current flow as high.

04․ The current flow through electrolyte is due to the movement of

The ions move from an area of high energy toward an area of low energy in the electrolyte that produces a flow of electrons (current). Basically, this movement of ions is called as electrolytic conduction.

05․ When the battery is being charged, the terminal voltage decreases with
increasing charging rate.
increasing state of charge.
increasing temperature.
none of these.

Whenever a battery is being charged, the terminal voltage of the battery changes a small amount whenever the battery temperature changes. As the battery temperature increases, its terminal voltage decreases or as the terminal voltage decreases, its temperature increases. This is usually called as temperature compensation in a storage battery.

06․ Two battery having unequal emf
cannot be connected in parallel.
cannot be connected in series.
both a and d
can be connected in series only.

We cannot connect the two batteries in parallel, when they have unequal voltage. If we connect them in parallel, then the low voltage battery will be charged by the high voltage battery. So, there is a chance of causing damage to the circuit. But, if we connect them in series, then both voltages are added together and we get that added voltage at output side. Hence, two batteries having unequal voltage can be connected in series only.

07․ Battery charging equipment is generally installed
in well ventilated location.
in clean and dry place.
as near as practical to the battery being charged.
in location having all above features.

The ventilation is required to maintain the temperature level in battery. The clean and dry place protects the battery from short circuit by wet condition. The charging source should be as near as possible to the battery. Otherwise, more power loss occurs in the electrical wire. Hence, we need all the above features to install the battery charging equipment.

08․ Cell short circuit results in
low specific gravivity.
abnormal high temperature.
reduced gassing on charge.
all of above.

Due to the short circuit, sudden discharge happens. This is directly proportional to specific gravity. So, it decreases. Due to high current flow and sudden voltage drop, the temperature increases. The formation of hydrogen and oxygen in the electrolyte reduces. Hence, all of the above happens when the cell gets short circuit.

09․ Electrolyte for silver plating is
potassium nitrate solution.
dilute sulphuric acid.
double cyanide of silver and potassium solution.
any of above.

Basically in the silver plating method, the silver bar acts as the anode, the object is to be plated acts as the cathode and the double cyanide of potassium and silver acts as the electrolyte. When the direct current is passed between the anode and the cathode, the positive silver ions (Ag+) from the double cyanide of silver and potassium solution to the negative anode (the object), where they are neutralized by the electrons and stick to the object as silver metal.

10․ For cadium plating electrolyte used is
cadmium sulphate and sulphuric acid.
cadmium hexa metaphosphate.
sodium cyanide, cadmium and caustic soda.
any of above.

The cadmium plating electrolyte contains the sodium cyanide and a cadmium salt in the presence of another alkali compound, such as caustic soda or sodium carbonate. Usually the cadmium plating electrolyte is added in the following ratio of the sodium cyanide, cadmium and caustic soda. That is 30 grams of cadmium cyanide, 50 grams of sodium cyanide and 20 grams of caustic soda per litre of electrolyte solution.