FBISE, NCP & NBF-aligned resources for Classes 9–12
Browse by Class
Browse by Type
Physics Chapter 11 : Topic 9
Kirchhoff’s First Law
1 / 35
Kirchhoff’s first law states that at any junction in an electrical circuit:
Reasoning: Kirchhoff’s first law states that the algebraic sum of currents at a junction is zero, meaning incoming current equals outgoing current.
2 / 35
Kirchhoff’s first law is based on the principle of conservation of:
Reasoning: Charge cannot be created or destroyed, so the total current entering a junction must equal the total current leaving it.
3 / 35
A junction in an electrical circuit is a point where:
Reasoning: A junction is a point where current divides or combines due to multiple connected branches.
4 / 35
The mathematical form of Kirchhoff’s first law is:
Reasoning: The algebraic sum of currents at a junction is zero.
5 / 35
At a junction, $\mathbf{5\ A}$ and $\mathbf{3\ A}$ currents enter. If $\mathbf{6\ A}$ leaves through one branch, thecurrent leaving through another branch is:
Reasoning: Total incoming current $\ = \ $ total outgoing current.$\mathbf{5 + 3 = 6 + I}$ $\mathbf{\Longrightarrow}$ So, $\mathbf{I = 2\ A}$
6 / 35
Kirchhoff’s first law implies that:
Reasoning: If charge accumulated at a junction, conservation of charge would be violated.
7 / 35
In a circuit junction, if $\mathbf{10\ C}$ of charge enters per second, the total charge leaving per second must be:
Reasoning: Current represents charge flow per second, and charge conservation requires equal incoming and outgoing charge.
8 / 35
Kirchhoff’s first law applies to:
Reasoning: The junction law applies to all electrical circuits where branches meet.
9 / 35
If $\mathbf{12\ A}$ current enters a junction and two currents of $\mathbf{7\ A}$ and $\mathbf{3\ A}$ leave, the remaining outgoing current is:
Reasoning: $\mathbf{12 = 7 + 3 + I}$ $\mathbf{\Longrightarrow}$ So, $\mathbf{I = 2\ A}$
10 / 35
The reason current is conserved at a junction is that:
Reasoning: Kirchhoff’s first law directly follows from conservation of electric charge.
11 / 35
A student says, “More current leaves a junction than enters it”. This statement violates:
Reasoning: Excess current leaving would mean charge is disappearing from the junction.
12 / 35
In Kirchhoff’s first law, currents entering a junction are usually considered:
Reasoning: A common sign convention takes entering currents as positive and leaving currents as negative.
13 / 35
At a junction, the algebraic sum of currents is zero because:
Reasoning: The net current at a junction is zero due to charge conservation.
14 / 35
A circuit has three branches meeting at a point. Currents of $\mathbf{4\ A}$, $\mathbf{6\ A}$, and $\mathbf{2\ A}$ enter the junction. The total outgoing current is:
Reasoning: Total incoming current $\mathbf{= 4 + 6 + 2 = 12\ A}$So, outgoing current must also be $\mathbf{12\ A}$.
15 / 35
Kirchhoff’s first law does not directly involve:
Reasoning: The first law concerns current and charge conservation, not voltage.
16 / 35
If current entering a junction is greater than current leaving it, then:
Reasoning: Excess incoming charge would accumulate at the junction.
17 / 35
A current of $\mathbf{15\ A}$ divides into two branches. If one branch carries $\mathbf{9\ A}$, the other branch carries:
Reasoning: By Kirchhoff’s first law, $\mathbf{(15 = 9 + I)}$ $\mathbf{\Longrightarrow}$ So, $\mathbf{I = 6\ A}$
18 / 35
Kirchhoff’s first law can be written as:
Reasoning: It states that current entering a junction equals current leaving it.
19 / 35
A junction receives currents of $\mathbf{2\ A}$, $\mathbf{5\ A}$ and $\mathbf{8\ A}$. If $\mathbf{10\ A}$ leaves, the remaining outgoing current is:
Reasoning: Total incoming $\mathbf{= 2 + 5 + 8 = 15\ A}$Remaining outgoing $\mathbf{= 15 - 10 = 5\ A}$
20 / 35
The current at a junction is conserved because:
Reasoning: Current is the rate of flow of charge, and charge conservation requires balance.
21 / 35
Which physical quantity does Kirchhoff’s first law conserve?
Reasoning: The law is a direct consequence of charge conservation.
22 / 35
In a steady-state circuit, charge:
Reasoning: Steady current requires no net charge buildup at any point.
23 / 35
If $\mathbf{20\ A}$ current enters a junction and $\mathbf{12\ A}$ leaves, the remaining outgoing current must be:
Reasoning: $\mathbf{(20 = 12 + I)}$ $\mathbf{\Longrightarrow}$ Therefore, $\mathbf{I = 8A}$
24 / 35
Kirchhoff’s first law is also known as:
Reasoning: It is called the junction law because it applies at circuit junctions.
25 / 35
Which situation would violate Kirchhoff’s first law?
Reasoning: Charge cannot continuously accumulate at a junction in a steady circuit.
26 / 35
In a circuit, currents are assigned signs according to Kirchhoff’s first law because:
Reasoning: Sign convention helps express incoming and outgoing currents mathematically.
27 / 35
A junction has currents: $\mathbf{8\ A}$ entering, $\mathbf{5\ A}$ leaving, and another current leaving. The second outgoing current is:
Reasoning: $\mathbf{(8 = 5 + I)}$ $\mathbf{\Longrightarrow}$ So, $\mathbf{I = 3\ A}$
28 / 35
Kirchhoff’s first law is valid because electrons:
Reasoning: Electric charge carried by electrons is conserved.
29 / 35
In a complex circuit, Kirchhoff’s first law helps determine:
Reasoning: The law provides equations relating currents at junctions.
30 / 35
The most accurate statement about Kirchhoff’s first law is:
Reasoning: The law applies specifically to current balance at junctions due to charge conservation.
31 / 35
A circuit junction has three incoming currents of $\mathbf{2\ A}$, $\mathbf{4\ A}$, and $\mathbf{6\ A}$. Two outgoing currents are $\mathbf{5\ A\ }$and $\mathbf{4\ A}$. The third outgoing current is:
Reasoning: Total incoming $\mathbf{= 12\ A}$ ; Outgoing already $\mathbf{= 9\ A}$ ; Remaining $\mathbf{= 3\ A}$
32 / 35
Kirchhoff’s first law would fail if:
Reasoning: The law depends on conservation of charge.
33 / 35
The conservation of charge means that in a closed electrical system:
Reasoning: Charge cannot be created or destroyed.
34 / 35
A junction is sometimes called a node because:
Reasoning: A node or junction is a connection point of two or more circuit branches.
35 / 35
Kirchhoff’s first law is essential in circuit analysis because it allows:
Reasoning: The junction law provides relationships between currents in complex circuits.
Your score is
Restart quiz
