Worksheet: Ohm’s Law

In this worksheet, we will practice using the formula V = IR (Ohm's law) to work out the values of the potential difference, current, and resistance in simple circuits.

Q1:

A resistor in a circuit has a potential difference of 20 V across it. The current through the resistor is 0.4 mA. What is the resistance of the resistor?

Q2:

Which of the following is the correct unit for potential difference?

  • AOhm
  • BAmpere
  • CJoule
  • DWatt
  • EVolt

Q3:

How many volts are there in 20 kilovolts?

Q4:

A resistor in a circuit has a potential difference of 10 V across it. The current through the resistor is 10 A. What is the resistance of the resistor?

Q5:

What kind of circuit component has a lower resistance if the temperature around the component is higher?

  • AAn ohmic conductor
  • BAn LED
  • CA fuse
  • DA diode
  • EA thermistor

Q6:

How many millivolts are there in 0.5 volts?

Q7:

Liam wants to find out the resistance of a resistor. He connects the resistor to a variable potential difference power source and uses an ammeter to find the current through the resistor. His results are shown in the table.

Potential Difference (V) 3 6 9 12 15
Current (mA) 50 100 150 200 250

Q8:

A student has a resistor of unknown resistance. She places the resistor in series with a source of variable potential difference. Using an ammeter, she measures the current through the resistor at different potential differences and plots her results on the graph as shown in the diagram. What is the resistance of the resistor?

Q9:

Ammeters should always be connected in . Voltmeters should always be connected in .

  • Aseries, series or parallel
  • Bparallel, parallel
  • Cseries, series
  • Dseries, parallel
  • Eparallel, series

Q10:

What kind of circuit component has a lower resistance if the light incident upon it is at a higher intensity?

  • AAn LED
  • BA thermistor
  • CA fuse
  • DAn LDR
  • EA diode

Q11:

Which of the following is the correct unit for electrical resistance?

  • AVolt
  • BJoule
  • CWatt
  • DAmpere
  • EOhm

Q12:

A 2,300 Ξ© resistor in a circuit has a current of 100 mA through it. What is the potential difference across the resistor?

Q13:

Which of the following is the correct formula for Ohm’s Law?

  • A 𝑉 = 𝑅 𝐼
  • B 𝑉 = 𝐼 𝑅 
  • C 𝑉 = 𝐼 𝑅
  • D 𝑉 = 𝐼 + 𝑅
  • E 𝑉 = 𝐼 𝑅

Q14:

A 10 Ξ© resistor in a circuit has a potential difference of 5 V across it. What is the current through the resistor?

Q15:

The diagram shows three graphs. Each graph shows the current through a component against the potential difference across it.

Which graph shows the characteristics of an ohmic conductor?

  • A(A)
  • B(C)
  • C(B)

Which graph shows the characteristics of a diode?

  • A(A)
  • B(B)
  • C(C)

Q16:

What is wrong with the circuit shown in the diagram?

  • AThe signs of the battery are the wrong way around.
  • BVoltmeters and ammeters must always be used together.
  • CThe voltmeter will lower the resistance of the circuit.
  • DVoltmeters should be connected in parallel across a component.
  • EThe current is shown as flowing in the wrong direction.

Q17:

What is wrong with the circuit shown in the diagram?

  • AThe current is shown as flowing in the wrong direction.
  • BThe current will be different on each side of the resistor; therefore, the ammeter cannot give a reading.
  • CAmmeters and voltmeters must always be used together.
  • DAmmeters should not be connected in parallel.
  • EThe signs of the battery are the wrong way around.

Q18:

A student sets up the circuit shown in the diagram. She uses an ammeter to measure the current through the circuit and gets a value of 2.5 A. She then uses a voltmeter to measure the potential difference across the resistor and gets a value of 10 V. What is the value of the resistance of the resistor?

Q19:

The diagram shows a circuit consisting of a cell providing a potential difference of 20 V and a resistor with a resistance of 5 Ξ©. What is the current through the resistor?

Q20:

A student sets up the circuit shown in the diagram. He sees that the ammeter reads 0.05 A. What value does the voltmeter read?

Q21:

How many ohms are there in 1 kilohm?

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