The circuit diagram in figure shows three resistors 2 Ω, 4 Ω and R Ω connected to a battery of e.m.f. 2V and internal resistance 3 Ω. If main current of 0.25 A flows through the circuit, find —
(a) the p.d. across the 4 Ω resistor
(b) the p.d. across the internal resistance of the cell,
(c) the p.d. across the R Ω or 2 Ω resistor, and
(d) the value of R.

Question

The circuit diagram in figure shows three resistors 2 Ω, 4 Ω and R Ω connected to a battery of e.m.f. 2V and internal resistance 3 Ω. If main current of 0.25 A flows through the circuit, find —
(a) the p.d. across the 4 Ω resistor
(b) the p.d. across the internal resistance of the cell,
(c) the p.d. across the R Ω or 2 Ω resistor, and
(d) the value of R.

KnowledgeBoat · Accepted Answer

(a) Given, resistor = 4 Ω I = 0.25 A the p.d. across the 4 Ω resistor (V) = ? Using Ohm's law V = IR Substituting the values in the formula above we get, V = 0.25 x 4 = 1 V Hence, the p.d. across the 4 Ω resistor (V) = 1 V (b) Given, internal resistance = 3 Ω I = 0.25 A the p.d. across the internal resistance of the cell = ? Using Ohm's law V = IR Substituting the values in the formula above we get, V = 0.25 x 3 = 0.75 V Hence, the p.d. across the internal resistance (V) = 0.75 V (c) Potential difference across R Ω or 2 Ω V = V_net - V_{across 4 Ω} - V_{across 3 Ω} Hence, we get, V = 2 - 1 - 0.75 = 0.25 V (d) The p.d. across resistor of R Ω = 0.25 V Let the equivalent resistance of the resistors of 2 Ω and R Ω connected in parallel be R'_p Using Ohm's law V = IR 0.25 = 0.25 x R'_p Substituting the value of R'_p from above: Hence, value of R = 2 Ω

Physics

Current Electricity

Related Questions

A cell supplies a current of 1.2 A through two resistors each of 2 Ω connected in parallel. When the resistors are connected in series, it supplies a current of 0.4 A. Calculate (i) the internal resistance and (ii) e.m.f. of the cell.

Three resistors of 6.0 Ω, 2.0 Ω and 4.0 Ω are joined to an ammeter A and a cell of e.m.f. 6.0 V as shown in figure. Calculate —
(a) the effective resistance of the circuit, and
(b) the reading of ammeter.

The diagram below in figure shows the arrangement of five different resistances connected to a battery of e.m.f. 1.8 V. Calculate —
(a) the total resistance of the circuit, and
(b) the reading of ammeter A.

A battery of e.m.f. 16 V and internal resistance 2 Ω is connected to two resistors 3 Ω and 6 Ω connected in parallel. Find (a) the current through the battery (b) p.d. between the terminals of the battery (c) the current in 3 Ω resistor (d) the current in 6 Ω resistor.