Practice free Current Electricity (Physics) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
If an ammeter is to be used in place of a voltmeter then we must connect with the ammeter a :
If ammeter is used in place of voltmeter (i.e. in parallel) it may damage due to large current in circuit. Hence to control this large amount of current a high resistance must be connected in series.
A galvanometer of resistance 36 Ω is changed into an ammeter by using a shunt of 4 Ω. The fraction f0 of total current passing through the galvanometer is :
A galvanometer, having a resistance of 50 Ω gives a full scale deflection for a current of 0.05 A. The length in meter of a resistance wire of area of cross-section 2.97× 10–2 cm2 that can be used to convert the galvanometer into an ammeter which can read a maximum of 5 A current is (Specific resistance of the wire = 5 × 10–7 Ωm)
⇒ ⇒ .
An ammeter reads up to 1 ampere. Its internal resistance is 0.81 ohm. To increase the range to 10 A the value of the required shunt is :
⇒ .
The resistances of the four arms P, Q,R and S in a Wheatstone's bridge are 10Ω ,30Ω ,30Ω and 90Ω, respectively. The emf and internal resistance of the cell are 7 V and 5 Ω respectively. If the galvanometer resistance is 50Ω, the current drawn from the cell will be
(b) Effective resistance,
Reff=40x120/120+40=4800/160=30Ω
∴ Current I=7/(30+5)=7/35=0.2A
[∴ I=E/R+r]
Kirchhoff's junction rule is a direct consequence of the conservation of which physical quantity?
According to the provided text, 'Kirchhoff’s junction rule is based on conservation of charge and the outgoing currents add up and are equal to incoming current at a junction.' This highlights that the rule, stating the sum of currents entering a junction equals the sum of currents leaving it, is fundamentally about charge not accumulating at any point, hence conservation of charge.
Which of Kirchhoff's rules states that the algebraic sum of changes in potential around any closed loop must be zero?
The NCERT text explicitly states, '(b) Loop rule: The algebraic sum of changes in potential around any closed loop involving resistors and cells in the loop is zero'. This rule is a direct application of the conservation of energy, as potential difference is related to work done per unit charge.
When labelling a directed arrow for current 'I' in a resistor, if 'I' is determined to be negative after calculation, what does it signify?
The text explains: 'If ultimately I is determined to be positive, the actual current in the resistor is in the direction of the arrow. If I turns out to be negative, the current actually flows in a direction opposite to the arrow.'
For a cell with emf $e$ and internal resistance $r$, if the current $I$ flows from the negative terminal (N) to the positive terminal (P) through the cell, what is the potential difference $V = V(P) - V(N)$?
The context states, 'V = V(P) – V(N) = e – I r [Eq. (3.38) between the positive terminal P and the negative terminal N; I here is the current flowing from N to P through the cell].'
In the analysis of electric circuits using Kirchhoff's rules, when is it stated that there is no accumulation of charges at any junction or point?
The NCERT text clarifies: 'The proof of this rule [Junction Rule] follows from the fact that when currents are steady, there is no accumulation of charges at any junction or at any point in a line.'
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