Electricity

A battery of emf Ɛ and negligible internal resistance is connected in a circuit, as shown above. The resistances of R₁ and R₂ are high. Which ONE of the following combinations about the ammeter readings will be CORRECT when switch S is open and when switch S is closed?

• SWITCH OPEN : Ammeter reads only the current in R₁

  SWITCH CLOSED: Ammeter reads only the current in R2

• SWITCH OPEN : Ammeter reads only the current in R₂

  SWITCH CLOSED: Ammeter reads only the current in both R₁ and R₂

• SWITCH OPEN : Ammeter reads only the current in n both R₁ and R₂

  SWITCH CLOSED: Ammeter reads only the current in n both R₁ and R₂

• SWITCH OPEN : Ammeter reads only the current in n both R₁ and R₂

  SWITCH CLOSED: Ammeter reads only the current in R₂ only

Which ONE of the graphs below best represents the relationship between potential difference (V) and current (I) for an ohmic conductor?

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Four identical bulbs, P, Q, R and S, are connected to a cell in a circuit, as shown above. The cell has negligible internal resistance. Which ONE of the following statements about the brightness of bulbs P, Q, R and S is CORRECT?

• P burns brighter than R.

• S and Q burn brighter than P and R.

• P and R burn brighter than S and Q.

• ALL the bulbs burn with the same brightness

In the circuit diagram above, Rx and Ry are identical ohmic resistors connected in parallel. When the switch is open, the ammeter reading is 0,1 A and the voltmeter reading is 3 V. Ignore the internal resistance of the battery.

What will be the reading on the AMMETER and VOLTMETER when the switch is closed?

• READING ON AMMETER: Equal to 0,1

  READING ON VOLTMETER: Equal to 3 V

• READING ON AMMETER: Greater than 0,1

  READING ON VOLTMETER: Equal to 3 V

• READING ON AMMETER: Less than 0,1

  READING ON VOLTMETER: Less than 3 V

• READING ON AMMETER: Greater than 0,1

  READING ON VOLTMETER: Greater than 3 V

In the circuit diagrams above, the cells and resistors are identical. The cells have negligible internal resistances. The power dissipated in resistor X is P. The power dissipated in resistor Y is …

• $\frac{1}{4}P$

• $\frac{1}{2}P$

• $\frac{ }{ }2P$

• $\frac{ }{ }4P$

In the circuit diagram below, the resistance of resistor R₁ is TWICE the resistance of resistor R_2. The two resistors are connected in series and identical high-resistance voltmeters are connected across each resistor. The readings on the voltmeters are V₁ and V₂ respectively. Which ONE of the following statements concerning the voltmeter readings is CORRECT?

• V₁ = 2V₂

• V₁ = ½V₂

• V₁= ¼V₂

• 2V₁ = V₂

When a resistor of resistance R is connected to a battery of emf Ɛ and negligible internal resistance, the power dissipated in the resistor is P. If the resistor is replaced with a resistor of resistance 2R, without changing the battery, the power dissipated will be …

• ¼P

• ½P

• 2P

• 4P

The minimum value of the resistance that can be obtained by connecting two 4 Ω resistors is ...

• 1 Ω.

• 2 Ω.

• 3 Ω.

• 8 Ω.

Learners investigate the relationship between current (I) and potential difference (V) at a constant temperature for three different resistors, X, Y and Z. They obtain the graphs shown below. The resistances of X, Y and Z are R_X, R_Y and R_Z respectively. Which ONE of the following conclusions regarding the resistances of the resistors is CORRECT?

• R_z > R_Y > R_x

• R_X = R_Y = R_Z

• R_X > R_Y > R_Z

• R_X > R_Y and R_Y < R_Z

Three identical light bulbs are connected in a circuit as shown above. The resistances of the battery and connecting wires can be ignored. Which ONE of the following statements is CORRECT when switch S is closed?

The reading on V₁ is …

• half that on V₂.

• equal to that on V_2.

• twice that on V₂.

• three times that on V₂.