Problems on Electronics:

# Resistance: -

Ohm’s Law: - Given that the physical dimensions of the resistance are not changing, the amount of current passing through it is directly proportional to the amount of voltage applied across it’s end points.

The series and parallel combination of resistances: -

In the case of series combination the current flowing through each resistance remains constant and the voltage across it changes. In the case of parallel combination the voltage remains constant and the amount of current flowing through changes.

The effective resistance when N resistances are places in series with each other is given by:-

The effective resistance for N resistances in parallel is given as;-

The receptivity of any given substance is an important property and is defined as resistance per unit length per unit area.

## Capacitors:-

These are the devices, which store the charges for a definite amount of time. the strength of the capacitor to store the charges is called as capacitance. It is given by: -

The algebra of capacitors: -

- Find out the effective resistance when two resistance of 10 kohm each are connected in series and in parallel.
- Simplify the following circuit. Which of the following options are correct?
- Which of the following are correct:-
- In the case of parallel combination the effective resistance is less than the least.
- In the case of series combination the effective resistance is less than the least.
- In the case of parallel combination the effective resistance is greater than the greatest.
- In the case of series combination the effective resistance is greater than the greatest.

- Which of the following is correct?
- Receptivity is greater if the area of substance is greater.
- Receptivity is greater if the length of the substance is smaller.
- Receptivity is inversely dependent on the area and directly proportional to the length.
- Receptivity is directly proportional to the area and inversely proportional to the length of the substance.

- There are some substances whose resistance depends on the temperature. The equation governing this phenomenon is given as;-

The value of alpha is constant and is dependent on the substance. Draw the graphs of temperature versus resistance when

- Alpha is positive.
- Alpha is negative
- Alpha is zero.

- From the definition write down the equation for determining the receptivity of the substance.
- A wire is taken and stretched such that the length doubles and radius become half. What is the ratio of the initial to the final receptivity?
- The primary job of a capacitance is to store the charge. The charge is stored due production of opposite polarities of charges on two plates. Thus if a positive end of the supply is connected to right and negative end to the left then the right hand side becomes positive and left becomes negative. This the capacitor charges. What would happen if the A.C. current were provided to capacitor?
- It would produce a D.C. supply
- It will let the current go by.
- It will block the supply.
- None of the above.

- A capacitor filled with dielectric of constant 3 is having a length of plate as 3mm and breadth as 4 mm. What is the capacitance
- When dielectric medium is not preset?
- When dielectric medium is present?
- What is the relationship between capacitance of a capacitor filled with dielectric and not filled with dielectric? Can you write down a formula for the same?

- 10 capacitors are put in parallel with each other. The value of each capacitance is same say X microfarad. If a 11
^{th} capacitor of same strength is put by what amount the effective capacitance will change?