Fundamentals of Electrical Math

What is the formula for Ohm's Law?

Answer explanation

Ohm's Law states that voltage (V) is equal to the current (I) multiplied by the resistance (R), represented by the formula V = I × R. This is the correct choice among the options provided.

If a circuit has a current of 2 A and a resistance of 5 Ω, what is the voltage across the circuit?

• 5 V

• 10 V

• 15 V

• 20 V

Answer explanation

Using Ohm's Law (V = I × R), where I = 2 A and R = 5 Ω, we calculate V = 2 A × 5 Ω = 10 V. Therefore, the voltage across the circuit is 10 V.

Which formula is used to calculate electrical power?

Answer explanation

The formula for electrical power is given by P = I × V, where P is power, I is current, and V is voltage. This formula directly relates power to the product of current and voltage, making it the correct choice.

In a series circuit, how is the total resistance calculated?

Answer explanation

In a series circuit, the total resistance is simply the sum of all individual resistances. Therefore, the correct formula is R_{total} = R_1 + R_2 + R_3 + ... which adds each resistor's value together.

What is the main difference between AC and DC current?

• AC current flows in one direction, while DC current changes direction periodically.

• AC current changes direction periodically, while DC current flows in one direction.

• AC current is used in batteries, while DC current is used in household outlets.

• AC current is more dangerous than DC current.

Answer explanation

The correct choice states that AC current changes direction periodically, while DC current flows in one direction. This fundamental difference defines their applications and behavior in electrical systems.

If a device uses 100 W of power and operates at 10 V, what is the current flowing through the device?

• 5 A

• 10 A

• 15 A

• 20 A

Answer explanation

To find the current, use the formula P = V × I. Rearranging gives I = P / V. Substituting the values: I = 100 W / 10 V = 10 A. Thus, the current flowing through the device is 10 A.

In a parallel circuit, how is the total resistance calculated?

Answer explanation

In a parallel circuit, the total resistance is calculated using the formula R_total = 1 / (1/R_1 + 1/R_2 + 1/R_3 + ...). This accounts for the reciprocal nature of resistances in parallel, leading to a lower total resistance.

What is the unit of electrical resistance?

• Volt

• Ampere

• Ohm

• Watt

Answer explanation

The unit of electrical resistance is the Ohm, which measures how much a material opposes the flow of electric current. Volt measures electric potential, Ampere measures current, and Watt measures power.

If a circuit has a voltage of 12 V and a current of 3 A, what is the power consumed by the circuit?

• 24 W

• 36 W

• 48 W

• 60 W

Answer explanation

Power is calculated using the formula P = V × I. Here, P = 12 V × 3 A = 36 W. Therefore, the power consumed by the circuit is 36 W.

Which of the following is a characteristic of DC current?

• It is used in household power supply.

• It is used in car batteries.

• It changes direction periodically.

• It is more efficient for long-distance transmission.

Answer explanation

DC current is commonly used in car batteries, providing a steady voltage for starting engines and powering electrical systems. Unlike AC, it does not change direction periodically, making it unsuitable for household power supply.