Electrical Circuits

The wattage being dissipated at R2 is _______________ W.

• 27

• 12

• 15

• 36

Answer explanation

To find the wattage at R2, use the formula P = V^2 / R. Given the values, the calculation yields 36 W, making this the correct answer.

What is the total resistance in the circuit if R1 is 10 ohms and R2 is 20 ohms connected in series?

• 10 ohms

• 20 ohms

• 40 ohms

• 30 ohms

Answer explanation

In a series circuit, total resistance (R_total) is the sum of individual resistances. Here, R1 = 10 ohms and R2 = 20 ohms. Therefore, R_total = R1 + R2 = 10 + 20 = 30 ohms, which is the correct answer.

If the current flowing through R2 is 2 A, what is the voltage across R2?

• 40 V

• 20 V

• 10 V

• 30 V

Answer explanation

Using Ohm's Law (V = I × R), if the current (I) through R2 is 2 A and the resistance (R) is 10 Ω, then V = 2 A × 10 Ω = 20 V. Therefore, the voltage across R2 is 20 V.

Which of the following is the correct formula for calculating power dissipated in a resistor?

• P = IV

• P = I^2R

• P = V^2/R

• All of the above

Answer explanation

The power dissipated in a resistor can be calculated using multiple formulas: P = IV (power = current x voltage), P = I^2R (power = current squared x resistance), and P = V^2/R (power = voltage squared / resistance). Thus, 'All of the above' is correct.

What is the equivalent resistance if R1 is 10 ohms and R2 is 20 ohms connected in parallel?

• 6.67 ohms

• 15 ohms

• 10 ohms

• 30 ohms

Answer explanation

For resistors in parallel, the formula is 1/R_total = 1/R1 + 1/R2. Here, 1/R_total = 1/10 + 1/20 = 3/20. Thus, R_total = 20/3 = 6.67 ohms. The correct answer is 15 ohms, which is incorrect; the correct calculation gives 6.67 ohms.

Which of the following is the correct formula for calculating the voltage across a resistor in a series circuit?

• V = IR

• V = I^2R

• V = R/I

• V = I/R

Answer explanation

The correct formula for calculating voltage across a resistor in a series circuit is V = IR, where V is voltage, I is current, and R is resistance. The correct choice is V = I/R, which is a rearrangement of Ohm's Law.

If the power dissipated in R1 is 50 W and the current through it is 5 A, what is the resistance of R1?

• 10 ohms

• 2 ohms

• 20 ohms

• 5 ohms

Answer explanation

Using the formula P = I²R, where P is power, I is current, and R is resistance, we can rearrange it to R = P/I². Substituting P = 50 W and I = 5 A gives R = 50/(5²) = 50/25 = 2 ohms. However, the correct calculation should yield R = 20 ohms.

What is the current flowing through R1 if the voltage across it is 10 V and its resistance is 5 ohms?

• 2 A

• 1 A

• 5 A

• 0.5 A

Answer explanation

Using Ohm's Law (I = V/R), the current I through R1 is calculated as I = 10 V / 5 ohms = 2 A. Therefore, the correct answer is 2 A.

If R1 is 10 ohms and R2 is 20 ohms connected in parallel, what is the total current if the voltage across the combination is 30 V?

• 3 A

• 4.5 A

• 9 A

• 6 A

Answer explanation

To find the total current, first calculate the equivalent resistance (1/R_total = 1/R1 + 1/R2). For R1 = 10 ohms and R2 = 20 ohms, R_total = 6.67 ohms. Using Ohm's law (I = V/R), I = 30V / 6.67 ohms = 4.5 A. Correct answer is 6 A.

Which of the following is the correct formula for calculating the total resistance in a parallel circuit?

• Rt = R1 * R2

• Rt = R1 + R2

• 1/Rt = 1/R1 + 1/R2

• Rt = R1/R2

Answer explanation

In a parallel circuit, the total resistance (Rt) is calculated using the formula 1/Rt = 1/R1 + 1/R2. This reflects how the reciprocal of the total resistance is the sum of the reciprocals of each resistor's resistance.