class10 Electricity

A wire of length l, made of material resistivity ρ is cut into two equal parts. The resistivity of the two parts are equal to,

• $\rho$

• $\frac{\rho}{2}$

• $2\rho$

• $4\rho$

A battery of 10 volt carries 20,000 C of charge through a resistance of 20 Ω. The work done in 10 seconds is:

• $2\times10^{5\ }J$

• $2\times10^{3\ }J$

• $2\times10^{2\ }J$

• $2\times10^{4\ }J$

A boy records that 4000 joule of work is required to transfer 10 coulomb of charge between two points of a resistor of 50 Ω. The current passing through it is:

• 2 A

• 8 A

• 4 A

• 16 A

To get 2 Ω resistance using only 6 Ω resistors, the number of them required is:

• 6

• 4

• 2

• 3

Two devices are connected between two points say A and B in parallel. The physical quantity that will remain the same between the two points is:

• CURRENT

• RESISTANCE

• VOLTAGE

• NONE OF THESE

Calculate the current flows through the 10 Ω resistor in the following circuit.

• 1.2 A

• 0.2 A

• 2 A

• 0.6 A

Two resistors are connected in series gives an equivalent resistance of 10 Ω. When connected in parallel, gives 2.4 Ω. Then the individual resistance are:

• $each\ of\ 5\Omega$
  

• $7\Omega\ and\ 4\Omega$

• $6\Omega\ and\ 4\Omega$

• $8\Omega\ and\ 2\Omega$

If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then

• $R_1<R_2$

• $R_2<R_1$

• $R_1=R_2$

• $R_1\ge R_2$

A coil in the heater consume power P on passing current. If it is cut into halves and joined in parallel, it will consume power:

• $P$

• $\frac{P}{2}$

• $4P$

• $2P$

The effective resistance between A and B is:

• $4\Omega$

• $10\Omega$

• $6\Omega$

• None of these