Science: Ohm's Law and Electric Circuits Worksheet

Question 1

A resistor has a resistance of 6 ohms and a current of 2 amperes flows through it. Find the voltage across the resistor.

Accepted Answer

The voltage is 12 volts because V = IR = 2 A x 6 ohms = 12 V.

Question 2

A 24 volt battery is connected to a resistor. The current in the circuit is 3 amperes. Find the resistance.

Accepted Answer

The resistance is 8 ohms because R = V / I = 24 V / 3 A = 8 ohms.

Question 3

A circuit has a resistance of 15 ohms and a voltage of 45 volts. Find the current.

Accepted Answer

The current is 3 amperes because I = V / R = 45 V / 15 ohms = 3 A.

Question 4

A lamp draws 0.5 amperes from a 120 volt source. What is the lamp's resistance?

Accepted Answer

The lamp's resistance is 240 ohms because R = V / I = 120 V / 0.5 A = 240 ohms.

Question 5

A device has a resistance of 10 ohms and is connected to a 9 volt battery. Find the current in the device.

Accepted Answer

The current is 0.9 amperes because I = V / R = 9 V / 10 ohms = 0.9 A.

Question 6

Two resistors of 4 ohms and 6 ohms are connected in series. Find the total resistance.

Accepted Answer

The total resistance is 10 ohms because resistances in series add directly: 4 ohms + 6 ohms = 10 ohms.

Question 7

Two resistors of 12 ohms and 18 ohms are connected in parallel. Find the equivalent resistance.

Accepted Answer

The equivalent resistance is 7.2 ohms because 1 / Req = 1 / 12 + 1 / 18 = 5 / 36, so Req = 36 / 5 = 7.2 ohms.

Question 8

A 20 volt source is connected to a series circuit containing a 3 ohm resistor and a 7 ohm resistor. Find the total current in the circuit.

Accepted Answer

The total current is 2 amperes because the total resistance is 3 ohms + 7 ohms = 10 ohms, and I = V / R = 20 V / 10 ohms = 2 A.

Question 9

A 12 volt battery is connected to two parallel resistors of 6 ohms and 3 ohms. Find the equivalent resistance of the circuit.

Accepted Answer

The equivalent resistance is 2 ohms because 1 / Req = 1 / 6 + 1 / 3 = 1 / 6 + 2 / 6 = 3 / 6 = 1 / 2, so Req = 2 ohms.

Question 10

A resistor has 18 volts across it and carries 3 amperes of current. How much power does it use?

Accepted Answer

The power is 54 watts because P = VI = 18 V x 3 A = 54 W.

Question 11

An electric heater uses 1200 watts when connected to a 120 volt outlet. Find the current drawn by the heater.

Accepted Answer

The current is 10 amperes because I = P / V = 1200 W / 120 V = 10 A.

Question 12

A phone charger delivers 5 volts and 2 amperes. Find its power output.

Accepted Answer

The power output is 10 watts because P = VI = 5 V x 2 A = 10 W.

Question 13

A student says that increasing resistance in a circuit with the same voltage will increase the current. Explain whether this statement is correct.

Accepted Answer

The statement is incorrect. If the voltage stays the same, increasing resistance decreases current because I = V / R.

Question 14

Describe the difference between a series circuit and a parallel circuit in terms of current and voltage.

Accepted Answer

In a series circuit, the same current flows through each component and the voltage is shared among the components. In a parallel circuit, each branch has the same voltage and the current splits among the branches.

Question 15

A 9 volt battery is connected to a resistor and the current is measured as 0.3 amperes. If the battery voltage stays the same and the resistance is doubled, what will the new current be?

Accepted Answer

The new current will be 0.15 amperes. Doubling the resistance cuts the current in half when the voltage stays constant, according to I = V / R.

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Science: Ohm's Law and Electric Circuits

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