Current & Circuits (SL IB Physics)

What is the definition of electric current?

A power cable X has resistance R and carries current I. A second cable Y has resistance 2R and carries current .

What is the ratio ?

Two resistors are connected to a cell.

Assuming both resistors are made from wires of the same length, which graph shows how the potential V varies along the line XY?

Four resistors are connected to a battery of e.m.f. 6 V as shown.

If the battery has negligible internal resistance, what is the current in the battery?

Which of the following cannot be the units for resistivity?

Three resistors are connected to a cell of e.m.f. 10 V and negligible internal resistance as shown.

What is the power dissipated in one of the 2 Ω resistors and in the whole circuit?

Three identical lamps, W, X and Y are connected to a cell of negligible internal resistance as shown.

When the switch is closed, each lamp is lit. Which of the following correctly describes the brightness of lamps W, X and Y when the switch is opened?

A science student who lives in the UK, where the mains voltage is 240 V, buys a light bulb marked 60 W which she uses in her bedroom. The student takes the lightbulb with her on a trip to Canada where the mains voltage is 100 V and also uses it there.

Which line correctly identifies the approximate power dissipated in the bulb in the UK and Canada?

A resistor R is connected to the terminals of a battery of emf 9.0 V and internal resistance r.

A charge of 240 C through the resistor in two minutes. The power dissipated in the resistor as a result is 1440 J. What is the internal resistance r of the battery?  

A battery of electromotive force ϵ delivers charge Q to the load resistance. Which of the following statements is correct?

The potential difference across the terminals of a battery is 5.0 V when the current is 1.0 A and 4.0 V when the current is 1.5 A. What is the emf of the battery and its internal resistance?

An electrical circuit is designed to measure the current I through a variable resistor R. The cell used in the circuit has an emf ϵ and an internal resistance r.

A graph shows the variation of  with R.

What is the magnitude of the gradient?

Which statement about terminal potential difference V and e.m.f. ϵ is incorrect?

Which of the following units for internal resistance is incorrect?

In the two circuits shown, only the internal resistances differ.

Which row in the table below correctly describes the potential difference across and power dissipated by the 3 Ω resistor? 

A cell of internal resistance r is connected to a variable resistor R.

Which of the following statements about the circuit is/are correct?

(1) If the resistance of R decreases, the terminal potential difference of the cell also decreases, but the power dissipated in the cell is large

(2) If the resistance of R is made very large, the current in the circuit is very small but most of the power supplied by the cell is dissipated by R

(3) If the resistance of R is made very small, then the lifetime of the cell reduces

What is the current reading on the ideal ammeter shown?

What is the current reading on the ideal ammeter shown?

A student is investigating the properties of cells made using lemons in parallel. They find that their lemon cell has an emf of 1.0 V and an internal resistance of 5000 Ω. 

What is the best estimate of the least number of lemons needed to light a bulb with a rating of 50 W and 8.0 V?

The diagram shows a cubical wire framework made from rigid, uniform copper wire. The wires all have the same length.

Points A and H are connected to the terminals of a 6.0 V power supply. Side AB has a resistance of 2.0 Ω.

Which line correctly identifies the total resistance of the network, the potential at F and the current in BC?

	total resistance / Ω	current in side BC / A	potential at F / V
A.		3.6	6.0
B.		0.6	2.4
C.		1.2	3.6
D.		0.6	6.0

The circuit shown includes three identical cylindrical resistors, with dimensions such that the cross-sectional area is 5 mm², the length is 20 cm and the resistance is R Ω.

When the switch is closed, the total resistance of the circuit is 5 kΩ.

What is the resistivity of the material that the resistors are made from?

The readings on both ammeters are zero. What are the values of X and Y?

A strain gauge is a device which measure force. An applied tension on a thin wire of known resistance changes the length and cross-sectional area so that the value of the resistance is changed in a predictable way (assuming that volume remains constant).

When the length of the wire is increased by 5 % what will be the effect on the resistance?

Two rods have the same length and resistance. One rod is made from copper and the other from aluminium.

Copper is three times as dense as aluminium but has half the value of resistivity.

Which of the following gives the correct value of ?

The identical resistors marked (i), (ii), (iii) and (iv) are connected as shown. The battery which has negligible internal resistance supplies a total power of 20 W. 

What is the power dissipated in resistor (iv)?

A circuit contains five identical resistors and four identical voltmeters. The reading on voltmeter V₁ is 8.0 V and the reading on voltmeter V₂ is 1.0 V. What are the readings on V₃ and V₄?

Five resistors of equal resistance are connected to a cell as shown. 

Which of the following is correct about the power dissipated P_X, P_Y and P_Z in resistors X, Y and Z respectively? 

	PX	PY	PZ
A.
B.
C.
D.

Two cells, X and Y, each with internal resistance 1.0 Ω, are connected in a circuit with two resistors as shown. 

Which of the following statements is not correct? 

A circuit contains two batteries, an external resistor and a motor, which is attached to a pulley that lifts a load. The direction of current in the circuit is indicated. 

Which of the following energy transformations most accurately describes the behaviour of the circuit? 

A pump is designed to move water through a certain height h such that the water flows back down, turning a paddle wheel. Such a system is often used to explain the operation of a battery in an electric circuit.

Which row in the table below best contrasts the work done by the pump and a battery? 

A 24 V solar panel charges a 12 V battery with internal resistance 0.10 Ω. 

Which of the following is correct? 

A cell has internal resistance r.

A graph of terminal potential difference V across the cell against current drawn from the cell I is shown. The scales are such that the length is equal to the length . A point P is chosen on the graph, such that  is a square. 

Which of the following statements is correct? 

Which of the following correctly describes the electromotive force of a cell? 

The figure shows how the e.m.f. of a simple generator varies with time. 

Which of the following statements is incorrect? 

Two almost identical lead-acid accumulator batteries, X and Y, are connected in a circuit as shown. 

The following information is provided: 

• When S₁ is closed and S₂ remains open, the millivoltmeter reads 60 mV
• When both S₁ and S₂ are closed, the reading on the millivoltmeter changes by 20 mV and the ammeter reads 5.0 A

What is the resistance of R?