In series combination of resistances —

1. p.d. is same across each resistance
2. total resistance is reduced
3. current is same in each resistance
4. all of the above are true

In parallel combination of resistances :

1. p.d. is the same across each resistance
2. current is the same in each resistance
3. total resistance is increased
4. all of the above are true

For parallel combination of resistances, which of the statements are correct ?

1. On I-V graph, the slope of line is more.
2. The potential difference across each resistance is same.
3. The current in a resistor is inversely proportional to the resistance.
4. All of the above

Write the expressions for the equivalent resistance R of three resistors R₁, R₂ and R₃ joined in (a) parallel, (b) series.