Current

    Current is the rate of flow of electric charge. It is measured in amperes (A). One ampere is equal to a flow of one coulomb of charge per second.

• Charge Carriers: In electrical circuits, the charge carriers are usually electrons. In electrolytes, they can be ions.
• The direction of Current:
• Conventional Current: Flows in the direction of positive charge movement (even though electrons flow in the opposite direction).
• Electron Flow: The actual direction of electron movement.

Types of Current

• Direct Current (DC): Current flows in only one direction. Examples: Batteries, and solar cells.
• Alternating Current (AC): Current changes direction periodically. Example: Household electricity supply.

Factors Affecting Current

• Voltage (V): The electrical potential difference that drives current. Higher voltage usually leads to higher current.
• Resistance (R): The opposition to the flow of current. Higher resistance leads to lower current.
• Material: Different materials have different conductivities, affecting how easily current flows through them.

Ohm's Law

• Formula: V = IR
• V = Voltage (volts)
• I = Current (amperes)
• R = Resistance (ohms)
• Explanation: Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance.

Study Notes

• Current is essential for the operation of electronic devices and circuits.
• Voltage is like the pressure that pushes electrons, while resistance is like the obstacle they encounter.
• Ohm's Law is a fundamental principle for electronic calculations.

Here are some Multiple Choice Questions for the topic Current. Practice well with the questions and get more marks for your exam.

1➤ Which of the following is the unit of electric current?

ⓐ Volt
ⓑ Ohm
ⓒ Watt
ⓓ Ampere

➤ Ampere

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2➤ What happens to the current in a circuit if the resistance is increased?

ⓐ It increases
ⓑ It decreases
ⓒ It stays the same
ⓓ It depends on the voltage

➤ It decreases

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3➤ Which type of current flows in only one direction?

ⓐ Alternating Current
ⓑ Direct Current
ⓒ Pulsed Current
ⓓ None of the above

➤ Direct Current

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4➤ According to Ohm's law, if the voltage in a circuit doubles while the resistance stays the same, what happens to the current?

It is halved
It doubles
It stays the same
It quadruples

➤ It doubles

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5➤ The instrument used to measure electric current is:

ⓐ Voltmeter
ⓑ Galvanometer
ⓒ Potentiometer
ⓓ Ammeter

➤ Ammeter

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6➤ A material having very low resistance is known as:

ⓐ Insulator
ⓑ Resistor
ⓒ Conductor
ⓓ Semiconductor

➤ Conductor

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7➤ The SI unit of electrical resistance is:

ⓐ Volt
ⓑ Ampere
ⓒ Ohm
ⓓ Watt

➤ Ohm

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8➤ In a parallel circuit, the total current is equal to:

ⓐ The current through the highest resistance
ⓑ The current through the lowest resistance
ⓒ The difference of the currents through each branch
ⓓ The sum of the currents through each branch

➤ The sum of the currents through each branch

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9➤ The direction of conventional current is:

ⓐ From positive to negative
ⓑ From negative to positive
ⓒ Always from the battery
ⓓ Random

➤ From negative to positive

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10➤ A fuse is used in an electrical circuit to:

ⓐ Control the flow of current
ⓑ Increase the voltage
ⓒ Protect against excessive current
ⓓ Convert AC to DC

➤ Protect against excessive current

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11➤ What is the current flowing through a 10-ohm resistor when it has a voltage of 100 volts across it?

ⓐ 1 amp
ⓑ 5 amps
ⓒ 10 amps
ⓓ 100 amps

➤ 10 amps

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12➤ Electrical power is calculated using the formula:

ⓐ P = IV
ⓑ P = I/V
ⓒ P = V/I
ⓓ All of the above

➤ All of the above

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13➤ Which of these materials has the highest resistance?

ⓐ Silver
ⓑ Copper
ⓒ Aluminum
ⓓ Plastic

➤ Plastic

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14➤ Kirchhoff's Current Law (KCL) states that:

ⓐ Voltage around a closed loop is zero
ⓑ Current in a series circuit is the same throughout
ⓒ The sum of currents entering a junction equals the sum of currents leaving it
ⓓ Resistance is directly proportional to voltage

➤ The sum of currents entering a junction equals the sum of currents leaving it

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15➤ A superconductor is a material that:

ⓐ Has a very high resistance
ⓑ Has a moderate resistance
ⓒ Is only conductive at high temperatures
ⓓ Has zero resistance

➤ Has zero resistance

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16➤ In a series circuit, if one bulb fails, what happens?

ⓐ All bulbs go out
ⓑ The other bulbs get brighter
ⓒ The other bulbs get dimmer
ⓓ Nothing happens to the other bulbs

➤ All bulbs go out

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17➤ The heating effect of current is used in devices like:

ⓐ Electric motors
ⓑ Electric heaters
ⓒ Generators
ⓓ Transformers

➤ Electric heaters

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18➤ What affects the resistance of a wire?

ⓐ Length
ⓑ Cross-sectional area
ⓒ Material
ⓓ All of the above

➤ All of the above

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19➤ A cell converts _____ energy into electrical energy.

ⓐ Heat
ⓑ Light
ⓒ Chemical
ⓓ Mechanical

➤ Chemical

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20➤ When resistors are connected in parallel, the overall resistance of the circuit:

ⓐ Increases
ⓑ Decreases
ⓒ Stays the same
ⓓ Depends on the values of the resistors

➤ Decreases

Connecting resistors in parallel provides multiple paths for current to flow. This effectively increases the total "area" for current to travel through, and as a result, the overall resistance decreases.

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