Electric current and ohm's law

a circuit consisting of a battery and a resistor. The current through the circuit is 50 mA.Over a period of 1.5 hours,how much charge flows in the circuit?

• 270 C

• 200 C

• 230 C

A laptop charger passes a current of 5.0 A through a laptop battery. Over a period of time, 45‎ ‎000 C of charge is transferred to the battery. For how many hours was the laptop left to charge?

• 2.5 hours

• 1.5 hours

• 3 hours

student has a resistor of unknown resistance. She places the resistor in series with a source of variable potential difference. Using an ammeter, she measures the current through the resistor at different potential differences and plots her results on the graph as shown in the diagram. What is the resistance of the resistor?

• 5 Ω

• 0.2 Ω

• 4 Ω

A 7 Ω resistor and a 5 Ω resistor are connected in series to a cell. The cell provides a current of 4 A through the circuit. How much energy do the resistors transfer to the surrounding environment in 20 seconds?

• 3840 J

• 192 J

• 1920 J

A bulb is connected to a cell in series. The potential difference across the bulb is 4 V and the current through it is 0.1 A

How much charge passes through the bulb in 60 seconds? And how much energy does the bulb dissipate as light and heat in such time?

Which conductor has larger conductivity?

• A

• B

• Same

A wire has the same resistance as the one given in the figure. Calculate its resistivity if the length of the wire is 10m and its area of cross section is 2m.

• 8 Ω.m

• 5 Ω.m

• 16 Ω.m

A material B has twice the specific resistance of the material A. A circular wire made of B has twice the diameter of the wire made of A. Then , for the two wires to have to have the same resistance, the ratio

L_a/L_b of their respective lengths is

• 1/2

• 2

• 1/4

• 4

If a wire is stretched to make it 0.1% longer, its resistance will

• increase by 0.2%

• increase by 0.05%

• Decrease 0.2%

• Decrease 0.05%