Electric circuits DBE grade 12 Part 1

Which ONE of the circuits below can be used to measure the current in conductor X and the potential difference across its ends?

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Ampere second could be the unit of

• power

• energy

• conductance

• charge

A circuit contains two unequal resistances in parallel; therefore:

• The current is the same in both.

• A larger current flows in the larger resistor

• The potential difference across each resistor is the same

• The smaller resistance has a smaller current flowing through it

Three equal resistors connected in a series across a source of emf together dissipate10 watts of power. What would be the power dissipated in the same resistors if they are connected in parallel across the same source of emf?

• 10 watts

• 30 watts

• 90 watts

• 270 watts

Five resistances are connected as shown below, and the combination is connected to a 40 V supply. What is the voltage between P and Q?

• 40 V

• 20 V

• 22,5 V

• 17,5 V

The current intensity in the circuit is 0,8 A and the voltage on the resistor is 20 V. What is the electrical power of this circuit?

• 0.04 W

• 16 kW

• 16 W

• 25 kW

Which of the following statements is true?

• Internal resistance mainly affects low-current loads

• Internal resistance mainly affects low-resistance loads

• Internal resistance mainly affects high-resistance loads

Which of the diagrams below represents a circuit in which the following 2 situations are possible?

When Switch S1 is on and Switch S2 is off, only light L1 will be on.

When Switch S1 is off and Switch S2 is on, neither light will be on.

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The current I in the figure is

• 1,5 A

• 0,5 A

• 3,5 A

• 2,5 A

The circuit diagram contains a combination of resistors R1, R2 and R3. The battery has an emf of 12 V and an unknown resistor (R).

When switch S is closed:

• Rexternal-decreases &

  Reading on ammeter A-

  increases

• Rexternal-decreases &

  Reading on ammeter A-

  remains constant

• Rexternal-decreases &

  Reading on ammeter A-

  decreases

• Rexternal-increases &

  Reading on ammeter A-

  increases