Electricity
Fundamental concepts of electric current, including Ohm's law, resistance, power, series and parallel circuits, and electrical properties of materials
Questions
Electric current is obtained from which part of an atom?
- Nucleus
- Negatively charged electrons
- Ionic compounds
- Positively charged protons
- Neutrons
Why does current flow more easily through a thick wire than a thin wire of the same material which is connected at a source?
- Resistance is inversely proportional to the area of cross-section
- Resistance is inversely proportional to length
- Resistance is directly proportional to the area of cross-section
- Thin wire has a larger diameter
- Thin wire has more capacity for the flow of electrons
Which of the following is true of electrical forces?
- Electric lines of force pass through a conductor.
- Electric lines of force exert lateral pressure to represent attraction between two like charges.
- Electrical lines of forces are produced by electrical charges.
- Electric lines of forces are parallel to the surface of a positively or negatively charged body.
- Electrical forces are weaker than gravitational forces.
What will be the resistance of a circuit when the connected battery will be of 1.5 V and the passing current is 15 A?
- 0.1 Ω
- 10 Ω
- 22.5 Ω
- 6.66 Ω
- 33.75 Ω
Calculate the current if the potential difference is increased to 120 V from 60 V with a current of 4 A from the source of a series circuit.
- 8 A
- 0.5 A
- 28,800 A
- 2 A
- 0.125 A
If a device has a resistance of 10 Ω and current of 3 A, then calculate the heat developed in 20 s.
- 18 J
- 1800 J
- 0.005 J
- 0.5 J
- 4.5 J
Which of the following properties of an alloy in a heating element used in a heater is true?
- An alloy does not consist of any metal
- Alloys decrease the tensile strength by adding a carbon agent.
- Alloys have very high resistance
- Alloy is designed to be able to operate at low temperatures.
- Alloys have a high melting point
When we connect any devices in series with a battery in the ON position, what will happen?
- Current is constant
- Voltage is constant
- Current gets divided
- Current is equal to zero
- Voltage is zero
Why are coils of electric irons made of an alloy instead of using pure metal?
- Alloys oxidise quickly
- Alloys are mechanically weak
- Alloys better withstand less heat before melting
- Alloys have low resistivity than pure metal
- Alloys have a higher melting point
Consider a conductor which passes 5 x 1016 electrons in 1 minute. Calculate the current flowing in the conductor.
- 0.133 mA
- 480 mA
- 7500 A
- 187.5 x 1035 A
- 0.0053 x 10-35 A
If the resistance of a wire is 30 Ω with a length of 3 m and diameter of 0.4 mm, then calculate the resistivity of the wire.
- 11.25 x 10-6 Ωm
- 1.25 x 10-6 Ωm
- 80 x 106 Ωm
- 0.0125 x 10-6 Ωm
- 0.0013 x 10-6 Ωm
The potential difference applied to a device is 5 KV. Calculate the number of electrons per second where current through it is 3.2 mA.
- 5.12 × 10-21
- 0.19 × 1021
- 2 × 1016
- 16.38 × 10-25
- 0.061 × 1025
If a device consumes energy 200 joules within a 4 second time period by providing a voltage of 120 V then calculate the power of the device.
- 50 Watts
- 800 Watts
- 0.02 Watts
- 2500 Watts
- 10000 Watts
Calculate the resistance of each 4 resistors connected in parallel in the circuit, carrying a current of 5 A with voltage of 250 V?
- 50 ohm
- 200 ohm
- 312.5 ohm
- 0.08 ohm
- 0.02 ohm
If voltage is 110 V in a circuit, which consists of a power of 1300 W then calculate the resistance.
- 15730 K Ohms
- 0.084 Ohms
- 9.3 Ohms
- 143 K Ohms
- 11.81 Ohms