Power in Circuits

A resistor of resistance R is connected to a fully charged cell of negligible internal resistance. A constant power P is dissipated in the resistor. An identical cell is connected in series with two identical resistors each of resistance R.

What is the power dissipated in each resistor?

• $P$

• $\frac{P}{2}$

• $\frac{P}{4}$

• $\frac{P}{8}$

A wire of length L is used in an electric heater. When the potential difference across the wire is 200 V, the power dissipated in the wire is 1000 W. The same potential difference is applied across a second similar wire of length 2L. What is the power dissipated in the second wire?

• 250 W

• 500 W

• 1000 W

• 2000 W

What power is dissipated in one of the 2Ω resistors?

• 4 W

• 2 W

• 1 W

• 0.5 W

What power is dissipated in the whole circuit?

• 8 W

• 4 W

• 2 W

• 1 W

A resistor of resistance 12 Ω is connected in series with a cell of negligible internal resistance. The power dissipated in the resistor is P. The resistor is replaced with a resistor of resistance 3.0 Ω. What is the power dissipated in this resistor?

• 4 P

• 2 P

• 16 P

• 0.25 P

In the circuits below the cells have the same emf and zero internal resistance. The resistors all have the same resistance.
Which of the following gives the ratio  $\frac{power\ dissipated\ in\ X}{power\ dissipated\ in\ Y}$  ?

•  $\frac{1}{4}$  

•  $\frac{1}{2}$  

•  $2$  

•  $4$  

Five resistors of equal resistance are connected to a cell as shown.

What is correct about the power dissipated in the resistors?

• The power dissipated is greatest in resistor X.

• The power dissipated is greatest in resistor Y.

• The power dissipated is greatest in resistor Z.

• The power dissipated is the same in all resistors

When an electric cell of negligible internal resistance is connected to a resistor of resistance 4R, the power dissipated in the resistor is P.

What is the power dissipated in a resistor of resistance value R when it is connected to the same cell?

• $\frac{P}{4}$

• $P$

• $4P$

• $16P$