CBSE Class 10 Answered

Direct Current:

1) It is derived from a cell or a battery and is uni-directional.

2) The positive and negative terminals are fixed.

3) The voltage v/s time graph is represented by a stariaght line parallel to time axis.

    Thus the value of voltage or current remains constant with time

Alternating Current:

1) The current changes its direction after equal intervals of time.

2) It has no fixed terminals as the current reverses its direction after every half cycle.

3) The voltage Vs time graph is generally represented by a sinusoidal curve.

ADVANTAGES of A.C. over D.C.

1. The generation of A.C. is cheaper than that of D.C.

2. A.C. machines are simple and do not require much repairs and maintenance during their use.

3. Wide range of voltages is obtained by the use of transformer.

4. The magnitude of current can be reduced by using an inductance or a conductor without any appreciable loss of energy

5. A.C. can easily be converted into D.C. with the help of rectifiers.

6. When A.C. is supplied at higher voltages in long distance transmission, the line losses are small compared to a D.C. transmission

DISADVANTAGES of A.C. over D.C.

1. Peak value of A.C. is high and it is dangerous to use so better insulation is required.

2. It attracts person who touches it unlike D.C. which gives a repelling shock.

3. An A.C. is transmitted from surface of the conductor and hence need several strands of thin wires insulated from each other.