The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then :

(1) The resistance will be doubled and the specific resistance will be halved

(2) The resistance will be halved and the specific resistance will remain unchanged

(3) The resistance will be halved and the specific resistance will be doubled

(4) The resistance and the specific resistance, will both remain unchanged

The following four wires are made of the same material and are at the same temperature. Which one of them has highest electrical resistance :

(1) Length = 50 cm, diameter = 0.5 mm

(2) Length = 100 cm, diameter = 1 mm

(3) Length = 200 cm, diameter = 2 mm

(4) Length = 300 cm, diameter = 3 mm

The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor is 

1. 21 × 10³ ± 10%

2. 23 × 10¹ ± 10

3. 21 × 10³ ± 5%

4. 12 × 10³ ± 5%

The potential difference between points A and B of the adjoining figure is

(1) $\frac{2}{3}V$

(2) $\frac{8}{9}V$

(3) $\frac{4}{3}V$

(4) 2 V

Two resistors of resistance R₁ and R₂ having R₁ > R₂ are connected in parallel. For equivalent resistance R, the correct statement is :

(1) $R>R_1+R_2$

(2) $R_1<R<R_2$

(3) $R_2<R<(R_1+R_2)$

(4) R < R₁

A wire of resistance R is divided into 10 equal parts. These parts are connected in parallel, the equivalent resistance of such connection will be:

1. 0.01R

2. 0.1R

3. 10R

4. 100R

Three resistors each of 2 ohm are connected together in a triangular shape. The resistance between any two vertices will be 

(1) 4/3 ohm

(2) 3/4 ohm

(3) 3 ohm

(4) 6 ohm

There are n similar conductors each of resistance R. The resultant resistance comes out to be x when connected in parallel. If they are connected in series, the resistance comes out to be :

(1) x/n²

(2) n²x

(3) x/n

(4) nx

Equivalent resistance between A and B will be 

(1) 2 ohm

(2) 18 ohm

(3) 6 ohm

(4) 3.6 ohm

Referring to the figure below, the effective resistance of the network is 

(1) 2r

(2) 4r

(3) 10r

(4) 5r/2